摘要:

Journal of the Chemical Society, Faraday Transactions I1 ISSN 0300-9238 J.C.S. FARADAY I1 AUTHOR INDEX VOL. 76 (1980) Alberti, Angelo, 948-53 Allen, Paul J., 785-93 Alper, Turhan, 205-16 Antheunis, Nicole, 324-9 Ashfold, Michael N. R., 905-14, 9 1 5-22 Atherton, Neil M., 660-6,822-6 Bailey, Raymond T., 633-47 Balanicka, Stefania, 42-8 Banerjee, Asok K., 620-32 Barber, Michael, 441-5 Barlow, A. John, 205-16 Basosi, Riccardo, 96-100 Batchelor, Peter J., 1610-17 Beatham, N., 929-35 Beevers, Martin S., 112-21 Bell, George M., 431-40 Bell, Ronald P., 954-60 Bernier, Jean Claude, 1224-33 Bhuiyan, Lutful B., 1388-408 Bieri, Gerhard, 67684 Bigot, Bernard, 1234-44 Bleijenberg, Karel C., 872-84 Borrell, Patricia M., 923-8,1442-9 Borrell, Peter, 923-8, 1442-9 Briano, Julio G., 812-21 Bridge, N.James, 472-89 Brzezinski, Bogumil, 1061-6 Buemi, Giuseppe, 490-5 Burrows, Hugh D., 685-92 Burtons, Brian, 1655-63 Calvert, Robert L., 1249-53 Campbell, Jeremy R., 1103-18 Canagaratna, S. Gnanaraj,11 19-27 Cape, J. Neil, 1646-54 Chadwick, David, 267-75 Champion, John V., 1610-17 Chan, Derek Y. C., 776-84 Chandramani, R., 1055-60 Cheah, Chew Toong, 7 1 1-28, 1543-60 Chiorino, Anna, 420-30 Chitaie, Shridhar M., 233-49 Chowdhury, Mihir, 620-32 Christie, Alec B., 267-75 Clark, Robin J. H., 1103-18 Claxton, Thomas A., 1655-63 Clifford, Anthony A., 735-46, 747-55 Clyne, Michael, A. A., 1569-85 Clyne, Michael A.A., 49-66, 177-96,369-82,405-19,71 1-28,961-78, 1275-92,1543-60,1561-8 Costa, Silvia M. de B., 1-13 Cox, A. Peter, 3304,339-50 Cox, Richard A,, 153-63 Cradock, Stephen, 496-505, 860-7 1 Cruickshank, Francis R., 633-47 AUTHOR INDEX, 1980 Cutler, Melvin, 756-60 Dalton, John, 88-95 Davis, Steven J., 961-78 Dawber, J. Graham, 1324-35 Dayan, Elie, 309-1 5 Delaney, John J., 506-19 Derzi, A. A., 319-23 Devaquet, Alain, 1234-44 Devaraj, N., 1055-60 Devriese, Annie, 767-75 De Wit, Hendrik G. M., 872-84 Dickinson, Eric, 1458-67 Dogonadze, R. R., 1128-46 Dong, Ronald Y., 57 1-3 Doran, Mark, 164-7 1,506- 19 Drillon, Marc, 1224-33 Dunbar, Robert C., 1079-83 Duncan, Ian A., 1415-28 Dunmur, David A., 309-15 Dunne, Lawrence J., 431-40 Duxbury, Geoffrey, 339-50 Dyke, John M., 1672-82 Eastwood, Andrew R., 704-10 Eldrup, Morten, 225-32 El-Issa, Basheer D., 441-5, 1375-80 Elliott, David Alan, 112-21 Ernsting, Nikolaus P., 844-59 Evans, Gareth J., 667-75 Evans, Myron, 1147-60 Evans, Myron W., 2 17-20, 286-301,542-9,667-75,76 1-6 Fattahallah, Ghisoon H., 556-70 Fayad, Noon K., 1672-82 Ferrario, Mauro, 542-9 Filippini, Giuseppe, 1336-46 Finsy, Robert, 767-75 Flint, Colin D., 82-7, 1381-7 Formosinho, Sebastiao J.,685-92 Fouassier, Monique, 2641 Fragala, I.L., 929-35 Freyland, Werner, 756-60 Fujisawa, Koichi, 895-904 Fujiwara, Shizuo, 1268-74 Gaggelli, Elena, 96-100 Gamer, C. David, 885-94 Garrone, Edoardo, 42&30 Gaylor, Kevin J., 1067-78 Gebhardt, Karl F., 1293-303 German, E.D., 1128-46 Gettins, John, 794-802, 1535-42 Ghiotti, Giovanna, 420-30 Gingerich, Karl A., 101-3 Glandt, Eduardo D., 812-21 Gooijer, Cees, 1664-71 Gould, Clive, 1535-42 Gramaccioli, Carlo M., 133646 Grant, Kevin R., 923-8, 1442-9 Gray, R. Walter, 205-16 Green, Jennifer C., 844-59 Grigolini, Paolo, 542-9,761-6 Grimson, Malcolm J., 1478-84 Guest, Martyn F., 506-19, 885-94 Gutman, Ivan, 1161-9 Haines, George, 1485-93 Hall, Denver G., 1254-67, 1535-42 Hamada, Fumiyuki, 895-904 Haque, Reza, 101-3 Hardy, Judith A., 339-50 Harriman, Anthony, 141 5-28, 142941,1618-26Harris, Dennis H.C., 1485-93 Harrison, Richard P., 785-93 Hawksworth, Roger W., 164-71, 506-19 Heaven, Michael C., 49-66, 177-96,40519,961-78 Hemingway, Stephen J., 936-47 Hillier, Ian H., 164-71, 506-19, 885-94 Hinchliffe, Alan, 172-6,441-5, 1375-80 Holub, Karel, 67-8 1 Horsewill, Anthony J., 660-6 Howarth, Oliver W., 1219-23 Hudson, Andrew, 948-53 Husain, David, 27685,606-19 Ihle, H. R., 447-52 Iqbal, Khalid, 1208-1 3 Itami, Toshio, 1347-53 Ivanov, I. B., 250-66 Jacobsen, Finn M., 225-32 Jaffe, Sigmund, 369-82 Jain, Rakesh K., 250-66 Jalonen, Jorma, 1450-7 Jamieson, Michael J., 1592-8 Jensen, David E., 1494-5 15 Jewess, Michael, 803-1 1 Jeyaraj, M., 589-97 Jobling, Paul L., 794-802, 1535-42 Johnson, Christopher A.F., 1409- 14 Johnstone, Walter, 633-47 Jose, Chalakkal I., 233-49 Josland, Graham D., 1672-82 Kamminga, Dik A., 1664-7 1 Kawashima, Yoshiyuki, 339-50 Kidd, Ian F., 172-6 Kim, Min G., 205-16 Klimo, Viliam, 1655-63 Kloster-Jensen, Else, 676-84 Knight, Michael J., 885-94 Koeksal, Fevzi, 550-5 Kornyshev, Alexey A., 67-8 1 Kryszewski, Marian, 351-68 Kuznetsov, A. M., 1128-46 Kvisle, Steinar, 676-84 Lamb, John, 205- 16 Landsberg, Barry M., 1208-13 J.C.S. FARADAY I1 AUTHOR INDEX VOL. 76 (1980) Langridge-Smith, Patrick R. R., 33&8 Law, Daniel, 13 14-23 Lee, Edmond P. F., 506-19,55&70,13 1423,1523-32 Lee-Bechtold, Susan, 803-1 1 Lekkerkerker, Hendrik, 767-75 Leuchs, Martin, 14-25 Levine, Samuel, 1388-408 Liddy, John P., 1569-85 Love, John D., 575-88 Luck, Werner A.P., 136-47 Lyus, Madeleine L., 556-70 MacDowell, Alastair A., 885-94 McKinley, John M., 979-1007 McLachlan, Roy J., 205-1 6 Maheswaran, Murugesapillai, 11 19-27 Maier, John P., 676-84 Malecki, Jerzy, 42-8, 197-204 Manterfield, Michael R., 309-1 5 Marconi, Giancarlo, 598-605 Marthaler, Oskar, 676-84 Martinez, Ernesto, 177-96, 405-19, 1275-92, 1561-8 Matthews, Anthony P., 1381-7 Meeten, Gerald H., 1610-17 Melo, E. C. C., 1-13 Meunier, Hubert, 1304-13 Meyer, Madeleine, 1586-91 Mielke, Zofia, 834-43 Milgrom, Lionel R., 88-95 Millefiori, Arcangelo, 827-33 Millefiori, Salvatore, 827-33 Mitchell, D.John, 776-84 Mitchell, David N., 785-93 Mogensen, Ola E., 225-32 Morris, Alan, 1672-82 Moseley, Michael E., 729-3 1 Murrell, John N., 319-23 Nadolski, Boguslaw, 351-68 Nagy-Felsobuki, Ellak, 148-52 Nakajima, Akio, 895-904 Ninham, Barry W., 776-84 North, Alastair M., 351-68 Nowak, Jadwiga, 42-8,197-204 Oberhammer, Heinz, 1293-303 Orchard, A. F., 929-35 Orlandi, Giorgio, 598-605 Osborne, Alexander D., 1627-37 1638-45 Outhwaite, Christopher W., 1388-408 Padel, Lilyane, 1224-33 Pailthorpe, Bernard A., 776-84 Paiva, M. Fernanda J. R., 68 5-92 Palacio, David J. D., 82-7 Pandey, Jata D., 1215-18 Papavassiliou, George C., 104-11 Parkinson, Gordon M., 1336-46 Pedulli, Gian Franco, 948-53 Peel, J.Barrie, 148-52 Perkins, Peter G., 520-33, 534-41 Pethrick, Richard A., 225-32, 351-68 Pettitt, Brian A., 571-3 Pfab, Josef, 844-59 Platts, Norman, 73546,747-55 Poggi, Gabriella, 598-605 Pons, B. Stanley, 979-1007 Porter, George, 1415-28, 1429-4 1 Potts, Anthony W., 506-19, 556-70,13 14-23, 1523-32 Price, Alun H., 217-20 Pugh, David, 633-47 Purdy, John R., 1304-13 Quinton, Alan M., 905-14, 915-22 Rakshit, Asit B., 1084-92 Ramakrishna, J., 1055-60 Ramdas, Subramaniam, 1336-46 1586-91 Rasburn, Eric J., 685-92 Rassing, Joergen E., 153542 Ratajczak, Henryk, 834-43 Ratcliffe, Christopher I.,1 196-207 Raudino, Antonio, 490-5 Reibnegger, Gilbert J., 1268-74 Reid, Colin J., 286-301 Richmond, Peter, 1478-84 Richoux, Marie Claude, 161 8-26 Ritchie, Geoffrey L.D., 648-59, 1245-8, 1249-53 Rivail, Jean Louis, 197-204 Robertshaw, John S., 1354-70 Rode, Bernd M., 1268-74 Roemelt, Joachim, 844-59 Ross, Dieter K., 575-88 Rowlinson, John S., 936-47,1468-77 Sastry, V. S. S., 1055-60 Schioeberg, Dag, 13647 Schmidt, Parbury P., 979-1007, 1008-25, 1026-44 Schwartz, Robert W., 620-32 Sen, Asok C., 620-32 Severin, Emery S., 936-47 Sevin, Alain, 1234-44 Shalabi, Ahmad S., 822-6 Shimoji, Mitsuo, 1347-53 Shiomi, Tomoo, 895-904 Siemann, Ulrich, 136-47 Simonetta, Massimo, 1336-46 Simons, John P., 905-14,915-22 Skea, Donald C. J., 860-71 Slater, Nigel K.H., 276-85, 606- 19 Smith, Edgar R., 1468-77 Smith, Ian W. M., 1354-70 Snook, Ian K., 1067-78 Sobhanadri, J., 589-97 Soerensen, Torben Smith, 1 170-95 Solomons, David P., 472-89 Speedy, Robin J., 693-703 Sridharan, K. R., 1055-60 Staveley, Lionel A. K., 803-1 1 Stead, Keith, 1045-9 Steiner, Erich, 391-404 Stevens, Robert, 330-8 Stewart, James J. P., 520-33, 534-41 Stilbs, Peter, 729-31 Tedder, John M., 1450-7, 1516-22 Thiebaut, Jean Marie, 197-204 Thiel, Walter, 302-8 Thomas, John M., 1336-46 Thornton, G., 929-35 Thrush, Brian A., 1304-1 3 Tiezzi, Enzo, 96-100 Tino, Jozef, 1655-63 Tranquille, Michel, 26-41 Tredwell, Colin J., 1627-37 Turner, David W., 1079-83 Turner, Paul H., 383-90 Twin, Robert J., 785-93 Tyndall, Geoffrey S., 153-63 Vander Donckt, Emile, 324-9 Van der Veken, Benjamin J., 1485-93 Van Megen, William J., 1067-78 Varandas, Antonio J.C., 129-35 Varma, Cyril A. G. O., 453-71 Velthorst, Nel H., 1664-71 Vidaud, Patrick, H., 1516-22 Vidaud, Patrick H., 1450-7 Visser, Robert J., 453-71 Vrbancich, Julian, 648-59, 1245-8 Walsh, Michael F., 794-802 Walton, Ian B., 885-94 Warneck, Peter, 1084-92 Wasylishen, Roderick E., 571-3 Watts, Robert O., 1067-78 Wayne, Richard P., 785-93 Webster, Brian C., 1592-8 Wheaton, Richard J., 1093-102, 1599-609 Whitefield, Philip D., 369-82, 71 1-28 Wierzejewska-Hnat, Maria, 834-43 Williams, Graham, 112-21 Williams, John M., 1045-9 Wright, Hilary J., 1409-14 WU, C.H., 47-52 Wyn-Jones, Evan, 794-802, 1535-42 Zdetsis, Aristides D., 104-1 1 Zecchina, Adriano, 420-30 Zeil, Werner, 1293-303 Zmbov, K., 447-52 Zuccarello, Felice, 490-5 Zundel, Georg, 14-25,1061-6 J.C.S. FARADAY I1 SUBJECT INDEX VOL. 76 (1980) SUBJECT INDEX, 1980 ABSORPTION Kinetics and photochemistry of the nitrate radical. Part 1. Absolute absorption cross section, 785-93 ACENAPTHOQUINONEStructure and fluxional behavior of the adducts of orthoquinones with organotin halides. An electron spin resonance study, 948-53 ACETATE Infrared investigation of water structure in desalination membranes, 136-47 Study of solvation models. Interpretation of solvent effect on the n* <-n transition of methyl acetate, 490-5 Charge-exchange mass spectra of ethyl acetate, methyl propionate, and propyl formate, 1450-7 ACETIC Polarizable acid-water hydrogen bonds with aqueous solutions of carboxylic acids, 14-25 Infrared studies of complexes between carboxylic acids and tertiary amines in argon matrixes, 834-43 ACETONE Evaluation of the van der Waals constant, internal pressure, and sound velocity in binary liquid mixtures from Flory's theory, 1215-1 8 ACETONITRILE Ionic and neutral optical emissions induced by helium(1cr) excitation of nitriles, 1079-83 ACETYL Microwave spectrum of acetyl isocyanate, 1208-1 3 ACETYLENE Emission spectra of the cations of cyanodiacetylene, methylcyanodiacetylene and ethylcyanodiacetylene in the gaseous phase.-A(d) +-X(rl) band systems, 676-84 Reactions of carbon dioxide, carbon dioxide dimer, and water cations with various neutral molecules, 1084-92 ACID Polarizable acid-water hydrogen bonds with aqueous solutions of carboxylic acids, 14-25 Theory of cooperative phenomena in monolayers of hydroxyhexadecanoic acid isqers, 43 1-40 Infrared studies of complexes between carboxylic acids and tertiary amines in argo matrixes, 834-43 Viscosity dependent internal conversion in the rhodamine dye, Fast Acid Violet 2& 1627-37 Internal conversion in the rhodamine dye, Fast Acid Violet 2R, 1638-45 ACTIVATION Magnetic susceptibility of expanded liquid selenium, 756-60 ADAM ANTANE Local configurations in cubic adamantane.Part 1, 1586-91 ADDITIVITY Magnetooptical studies of liquid mixtures. Part 4.Additivity of the Faraday effect, the magnetic rotation dispersion constant, and the excess magnetic rotation in binary liquid mixtures, 1324-35 ADDUCT Structure and fluxional behavior of the adducts of orthoquinones with organotin halides. An electron spin resonance study, 948-53 ADIPONITRILE Heat capacity of bis(adiponitrile)copper(I) nitrate. An order-disorder transition in a dilute system of nitrate ions, 803-1 1 ADIPONITRILECOPPER Heat capacity of bis(adiponitrile)copper(I)nitrate. An order-disorder transition in a dilute system of nitrate ions, 803-1 1 ADSORPTION Thermodynamic approach to the interpretation of electrokinetic data near the isoelectric point, 1254-67 ALBUMIN Ultrasonic relaxation studies of sodium octyl sulfate complexes with synthetic polymers and a protein in aqueous solution, 1535-42 ALC Study of self-association of tert-butyl alcohol by linear and nonlinear dielectric effects, 42-8 Infrared studies and thermodynamics of hydrogen bonding in 2-chloroethanol,3-chloropropanol and 4-chlorobutanol, 23349 Ultrasonic relaxation studies of sodium octyl sulfate complexes with synthetic polymers and a protein in aqueous solution, 1535-42 Intemal conversion-in the rhodamine dye, Fast Acid Violet 2R, 1638-45 ALIPH Magnetooptical studies of liquid mixtures.Part 4.Additivity of the Faraday effect, the magnetic rotation dispersion constant, and the excess magnetic rotation in binary liquid mixtures, 1324-35 J.C.S.FARADAY I1 SUBJECT INDEX VOL. 76 (1980) ALK Vibrational structure in the luminescence spectra of uranium-doped tungstates with ordered perovskite structure, 872-84 ALKALI Analysis of the vibrational spectrum of symmetrically solvated alkali metal cations, 979-1007 Hard-sphere model of fused salts, 1347-53 Helium I and helium I1 photoelectron spectra of alkali fluorides in the vapor phase, 1523-32 Indolyl alkali metal ion pairs in the excited state. Part 3. Solvent-excited solute relaxation in the S1-and TI-states, 1664-71 ALKANE Nonrigid molecules. Part 4. Hydrogen atom scrambling in the mass spectra of hydrocarbons, 88-95 ALKYL Far infrared solution spectra. Volume of rotation and effective torque, 286301 ALLYL Ionic and neutral optical emissions induced by helium(1a) excitation of nitriles, 1079-83 ALUMINUM Vibrational spectra of matrix isolated aluminum chloride dimer.Isotopic fine structure and valence force field, 26-4 1 Luminescence and 4A2-3 2E,2T1 absorption spectrum of hexaureachromium(II1) iodide and hexaureaalu- minum(II1) iodide :hexaureachromium(III), 82-7 AMINE Carbon-13 and nitrogen-14 nuclear magnetic resonance study of triethylenediamine, 57 1-3 Infrared studies of complexes between carboxylic acids and tertiary amines in argon matrixes, 834-43 Influence of screening of intramolecular easily polarizable hydrogen bonds on their infrared absorbance, 1061-6 The 4A2, <-> 2E, transitions in trans-dichlorobis(ethylenediamine)chromium( 1+ ) and trans- dichlorobis(1,3-diarninopropane)chromium( 1+), 138 1-7 AMINOETHANE Optical properties of [M(L-L)2M(L-L)2X2](ClO4)4, (M = platinum, palladium; L-L = 1,2liaminoeth-ane or 1,24iaminopropane; X = chlorine, bromine, iodine): bulk and small particles, 104-1 1 AMINOPROPANE Optical properties of [M(L-L)2M(L-L)2X2](ClO4)4, (M = platinum, palladium; L-L = 1,2-diaminoeth-ane or 1,2-diaminopropane; X = chlorine, bromine, iodine): bulk and small particles, 104-1 1 AMMONIA Reactions of carbon dioxide, carbon dioxide dimer, and water cations with various neutral molecules, 1084-92 Some model potentials for the ammoniated electron, 1592-8 AMMONIO Nuclear magnetic resonance spin-lattice relaxation and barriers in ethylenediammonium chloride, bromide, iodide, and sulfate, 1 196207 AMMONIUM Ultrasonic relaxation of surfactants in water and deuterium oxide solutions, 794-802 ANGLE Calculations on the ground states of hydrogen cyanide monocation and hydrogen isocyanide monocatio- n, 319-23 Power reflection spectroscopy near the Brewster angle.Molecular dynamics of liquids, 1 147-60 ANGULAR Contributions of orbital angular momentum to ligand hyperfine interactions in paramagnetic metal complexes, 660-6 ANILINE Effect of electric fields on the far infrared absorption cross section of liquid aniline, 667-75 Magnetooptical studies of liquid mixtures. Part 4. Additivity of the Faraday effect, the magnetic rotation dispersion constant, and the excess magnetic rotation in binary liquid mixtures, 1324-35 ANISOLE Electron spin resonance studies of ion association.Part 8. Effects of ion-pairing on nitrogen-14 hyperfine splittings in psubstituted nitrobenzene anions, 822-6 ANISOTROPY Quadrupole moment and magnetic anisotropy of carbon disulfide, 1245-8 ANTHRACENE Mechanismsof singlet energy transfer in doped anthracene crystals at 5 K, studied by nanosecond spectrofluorimetry, 472-89 Structure and dynamics of a new phase of anthracene, 1336-46 ANTHROATE Photodimerization of benzyl9-anthroate in the presence of triethylamine. Role of exciplex and triplet formation, 1-1 3 APPROXN Solvent structure in particle interactions. Low pressure effects and analytic limits, 776-84 AQIon-pairing in aqueous media.An exact solution for the interaction energy associated with two dielectric J.C.S. FARADAY I1 SUBJECT INDEX VOL. 76 (1980) AQ(contd)spheres, 575-88 ARGON Depolarized light scattering from gases of anisotropic molecules at intermediate pressures, 309-1 5 Energy transfer from state-selected photofragments. Electronic quenching of CS(AIII)V-e~, 91 5-22 Laser-excitation studies of bromine. Collisional energy transfer involving resolved quantum states of excited Br2B3II(OU+), 961-78 Laser-induced fluorescence studies: the B-X transition of chlorine. Part 5. Radiative lifetime of the B state, 1275-92 Quantum-resolved dynamics of excited states. Part 6. Radiative lifetime and collisional deactivation rates in bromine fluoride (B), 1569-85 AROM Far infrared solution spectra. Volume of rotation and effective torque, 286-301 Magnetooptical studies of liquid mixtures.Part 4. Additivity of the Faraday effect, the magnetic rotation dispersion constant, and the excess magnetic rotation in binary liquid mixtures, 1324-35 ASSOCN Study of self-association of tert-butyl alcohol by linear and nonlinear dielectric effects, 42-8 Static and dynamic Kerr-effect studies of glycerol in its highly viscous state, 112-21 Halide ion induced quenching and enhancement of the fluorescence of fluoranthene solubilized in cetyltrimethylammonium bromide micelles, 685-92 Electron spin resonance studies of ion association. Part 8. Effects of ion-pairing on nitrogen-14 hyperfine splittings in p-substituted nitrobenzene anions, 822-6 ATOM Kinetic study of the reactions of hydrogen and deuterium atoms with hydrogen bromide and deuterium bromide by time-resolved resonance fluorescence, 276-85 Kinetic study of ground state atomic nitrogen, N(24S3.2), by time-resolved atomic resonance fluorescence 60619 Reactions forming electronically-excited free radicals.Part 2. Formation of nitrogen 4S, 2D, and 2P atoms in the hydrogen atom + difluoroamidogen reaction, and nitrogen atom reactions, 1543-60 ATOMIZATION Atomization energies of the molecules LiSiO(g) and Si202(g) by mass spectrometric gaseous equilibriums 447-52 AZA COMPD Lowest excited states of aza-analogs of stilbene. INDO/S calculation, 598-605 BAND Study of the semiconductor-to-metal transition in vanadium dioxide and vanadium sesquioxide by ultraviolet photoelectron spectroscopy, 929-35 BARRIER Microwave spectrum and barrier to internal rotation of 2-methyl-2-nitropropane, 330-8 Microwave spectrum of acetyl isocyanate, 1208-1 3 Inelastic neutron scattering spectra of partially deuterated dimethylmethylphosphonates,1485-93 BASE Dielectric relaxation studies in some phenolic Mannich bases, 589-97 BASIS Cusped-Gaussian molecular wave functions.Part 3. Basis sets for the first-row atoms, 391-404 BEHAVIOR Viscous, viscoelastic and dielectric properties of a perfluorinated polymer, Krytox 143-AB, 205-1 6 BENZALDEHYDE Electron spin resonance studies of ion association. Part 8. Effects of ion-pairing on nitrogen-14 hyperfine splittings in p-substituted nitrobenzene anions, 822-6 BENZANTHRACENE External pressure effect on quenching of benz[a]anthracene and 9-cyanoanthracene fluorescence by dimethylmercury, 324-9 BENZENE High resolution ultraviolet photoelectron spectra of monohalo- and p-dihalobenzenes, 556-70 Quadrupole moments of benzene, hexafluorobenzene and other nondipolar aromatic molecules, 648-59 Thermodynamics of poly(dimethylsi1oxane) solutions, 895-904 Evaluation of the van der Waals constant, internal pressure, and sound velocity in binary liquid mixtures from Flory’s theory, 1215-18 BENZODITHIOPHENEDIONE Structure and fluxional behavior of the adducts of orthoquinones with organotin halides.An electron spin resonance study, 948-53 BENZONITRILE Source of anomalous fluorescence from solutions of 4‘-N,N’-dimethylaminobenzonitrile in polar solvents, 453-71 Electron spin resonance studies of ion association.Part 8. Effects of ion-pairing on nitrogen-14 hyperfine splittings in psubstituted nitrobenzene anions, 822-6 BENZOQUINONEPhotochemistry of manganese porphyrins. Part 3. Interconversion of manganese(I1) and manganese(III), 6 J.C.S. FARADAY I1 SUBJECT INDEX VOL. 76 (1980) BENZOQUINONE(contd)1415-28 Photochemistry of manganese porphyrins. Part 4. Photosensitized reduction of quinones, 1429-41 BENZYL Photodimerization of benzyl9-anthroate in the presence of triethylamine. Role of exciplex and triplet formation, 1-13 BERYLLIUM Further study of the beryllium monohydride radical by UHF-type and configuration interaction methods, 1655-63 BINDING Transition state model for water exchange in the first solvation shell of hydrated cations according to quantum chemical calculations, 1268-74 BIOL Marangoni instability at a spherical interface.Breakdown of fluid drops at low surface tension and cytokinetic phenomena in the living cell, 1170-95 BIPHENYL Diffusion equation for the nematic phase dielectric loss, 217-20 BIREFRINGENCE Theory of transient response for arbitrarily strong driving fields, 542-9 Quadrupole moments of benzene, hexafluorobenzene and other nondipolar aromatic molecules, 648-59 Quadrupole moment and magnetic anisotropy of carbon disulfide, 1245-8 Molecular quadrupole moment of naphthalene, 1249-53 Magnetic birefringence in liquids of near-isotropic molecules, 161&17 BLEACHING Kinetic matrix effects (response and density distribution functions): ring closure.Reaction of indolinobe- nzospiropyrans in glassy poly(alky1 methacrylates), 35 1-68 BLOCK Cusped-Gaussian molecular wave functions. Part 3. Basis sets for the fist-row atoms, 391-404 BOND Polarizable acid-water hydrogen bonds with aqueous solutions of carboxylic acids, 14-25 CH bond dipole, 172-6 Infrared studies and thermodynamics of hydrogen bonding in 2-chloroethanol,3-chloropropanol and 4-chlorobutanol, 233-49 Calculations on the ground states of hydrogen cyanide monocation and hydrogen isocyanide monocatio- n, 3 19-23 Microwave spectrum and barrier to internal rotation of 2-methyl-2-nitropropane7 330-8 Influence of screening of intramolecular easily polarizable hydrogen bonds on their infrared absorbance, 1061-6 Influence of unsaturated chromophore excitation on the feasibility and selectivity of adjacent CT bond cleavage, 1234-44 BONDING Infrared studies and thermodynamics of hydrogen bonding in 2-chloroethanol,3-chloropropanol and 4-chlorobutanol, 233-49 Dielectric relaxation studies in some phenolic Mannich bases, 589-97 Intramolecular hydrogen bond in ortho-hydroxyazobenzenes, 827-33 Zeeman effect of chlorine nuclear quadrupole resonance and hydrogen bonding in 2,6-, 2,5-, and 33- dichlorophenols, 1055-60 BORN Dynamic solvation.Ionic vibrations in nonstationary solvation shells, 102644 BORON Cusped-Gaussian molecular wave functions.Part 3. Basis sets for the fifst-row atoms, 391-404 BREWSTER Power reflection spectroscopy near the Brewster angle. Molecular dynamics of liquids, 1 147-60 BROMIDE Laser-induced fluorescence of iodine monobromide: the B~I'I(O +) excited state, 49-66 Optical properties of [M(L-L)2M(L-L>2X,](C104)4,(M = platinum, palladium; L-L = 1,24iaminoeth-ane or 1,2-diaminopropane; X = chlorine, bromine, iodine): bulk and small particles, 104-1 1 Kinetic study of the reactions of hydrogen and deuterium atoms with hydrogen bromide and deuterium bromide by time-resolved resonance fluorescence, 27685 Study of molecular motion in tert-butyl halides by pulsed proton magnetic resonance, 55&5 Halide ion induced quenching and enhancement of the fluorescence of fluoranthene solubilized in cetyltrimethylammonium bromide micelles, 685-92 Ultrasonic relaxation of surfactants in water and deuterium oxide solutions, 794-802 Nuclear magnetic resonance spin-lattice relaxation and barriers in ethylenediammonium chloride, bromide, iodide, and sulfate, 1196-207 BROMINE Quantum-resolved dynamics of excited states.Part 5. The long-lived ATI(l,) state of bromine, 177-96 Kinetics of excited states of bromine using laser excitation. Part 2. Radiative lifetime and collisional deactivation of the B3ll(O+,) state, 405-19 J.C.S. FARADAY I1 SUBJECT INDEX VOL. 76 (1980) BROMINE(contd)Laser-excitation studies of bromine.Collisional energy transfer involving resolved quantum states of excited Br2B3lI(Ou+), 961-78 Reactions of chlorofluoromethylene radicals studied by laser-induced fluorescence, 1304-1 3 Quantum-resolved dynamics of excited states. Part 6. Radiative lifetime and collisional deactivation -rates in bromine flioride (B), 1569-85 BROMOBENZENE High resolution ultraviolet photoelectron spectra of monohalo- and p-dihalobenzenes, 556-70 BROMOMETHANE SCF-Xo: study of the electronic structure of tetrahalomethanes, tetrahalosilanes, and tetrafluorogermane BROMONITROSOMETHANE Photoelectron spectra of nitrosomethane, tert-nitrosobutane and some perhalonitrosomethanes, 844-59 BROMOTRIFLUOROMETHANE Microwave spectra of bromotrifluoromethane and iodotrifluoromethane.Structures and dipole moments 339-50 BROMOTUNGSTATE Resonance Raman, infrared, and electronic spectral studies of p-oxo-decahalodimetallate speciesosmium, rhenium, ruthenium, and tungsten, 1 103-18 BROWNIAN Brownian dynamics of many-body systems, 1067-78 BUBBLE Thinning and rupture of ring-shaped films, 250-66 BUTANOL Infrared studies and thermodynamics of hydrogen bonding in 2-chloroethanol,3-chloropropanol and 4-chlorobutanol, 23349 BUTYL Study of self-association of tert-butyl alcohol by linear and nonlinear dielectric effects, 42-8 Study of molecular motion in tert-butyl halides by pulsed proton magnetic resonance, 55&5 CADMIUM Photoelectron spectra and valence shell electronic structure of zinc and cadmium difluoride, 13 14-23 CALCN Electronic structure and valence ionization energies of trichlorooxochromium studied by ab initio and SW-Xo: methods, 164-7 1 CH bond dipole, 172-6 Multipole analysis of MNDO results, 302-8 Lowest excited states of ma-analogs of stilbene.INDO/S calculation, 598-605 Electronic structure and assignment of the ultraviolet photoelectron spectra of 6-methyl-2-0x0-pyridine complexes of dichromium(I1) and dimolybdenum(II), 885-94 Prediction of phase equilibriums using the Redlich-Kwong equation of state, 1045-9 CAPACITANCE Theory of the electric double layer using a modified Poisson-Boltzmann equation, 1388-408 CAPACITY Heat capacity of bis(adiponitrile)copper(I)nitrate. An order-disorder transition in a dilute system of nitrate ions, 803-1 1 Hard-sphere model of fused salts, 1347-53 CARBIDE Atomization energies of complex gaseous yttrium carbides, 10 1-3 CARBON CH bond dipole, 172-6 Depolarized light scattering from gases of anisotropic molecules at intermediate pressures, 309-1 5 Microwave spectrum and barrier to internal rotation of 2-methyl-2-nitropropane, 330-8 Cusped-Gaussian molecular wave functions.Part 3. Basis sets for the first-row atoms, 391-404 Carbon-1 3 and nitrogen-14 nuclear magnetic resonance study of triethylenediamine, 57 1-3 On the NH proton tunneling rate in meso-tetraphenylporphine,729-31 Energy disposal in the vacuum ultraviolet photodissociation of carbon disulfide and carbon diselenide, 905-14 Energy transfer from state-selected photofragments. Electronic quenching of CS(A~II),.O_S, 91 5-22 Reactions of carbon dioxide, carbon dioxide dimer, and water cations with various neutral molecules, 1084-92 Carbon-1 3 nuclear magnetic resonance study of molecular motions in natural rubber, 1219-23 Quadrupole moment and magnetic anisotropy of carbon disulfide, 1245-8 Vibrational energy transfer from carbon monoxide (v = l), nitrogen (v = 1) carbon dioxide(001), nitrous oxide(001), and carbonyl sulfide(001) to ozone, 1354-70 CARBONYL Depolarized light scattering from gases of anisotropic molecules at intermediate pressures, 309-1 5 Reactions of carbon dioxide, carbon dioxide dimer, and water cations with various neutral molecules, 1084-92 Vibrational energy transfer from carbon monoxide (v = l), nitrogen (v = 1) carbon dioxide(001), 8 J.C.S.FARADAY I1 SUBJECT INDEX VOL. 76 (1980) CARBONYL(contd)nitrous oxide(001), and carbonyl sulfide(001) to ozone, 1354-70 CARBOXYLIC Polarizable acid-water hydrogen bonds with aqueous solutions of carboxylic acids, 14-25 CATION Calculations on the ground states of hydrogen cyanide monocation and hydrogen isocyanide monocatio- n, 319-23 Edssion spectra of the cations of cyanodiacetylene, methylcyanodiacetylene and ethylcyanodiacetylene in the gaseous phase. -A(d) -+ -X(d) band systems, 676-84 Analysis of the vibrational spectrum of symmetrically solvated alkali metal cations, 979-1007 Vibrational spectrum of alkali metal cations in distorted solvation shells.A prediction, 1008-25 Ionic and neutral optical emissions induced by helium(1a) excitation of nitriles, 1079-83 Reactions of carbon dioxide, carbon dioxide dimer, and water cations with various neutral molecules, 1084-92 Transition state model for water exchange in the first solvation shell of hydrated cations according to quantum chemical calculations, 1268-74 CD Absorption, circular dichroism and magnetic circular dichroism spectra of trisodium praseodymium tris(oxydiacetate) di(sodium perchlorate) hexahydrate, 62CL32 CELL Marangoni instability at a spherical interface. Breakdown of fluid drops at low surface tension and cytokinetic phenomena in the living cell, 1170-95 CELLULOSE Infrared investigation of water structure in desalination membranes, 136-47 CESIUM Ultrasonic relaxation of surfactants in water and deuterium oxide solutions, 794-802 Helium I and helium I1 photoelectron spectra of alkali fluorides in the vapor phase, 1523-32 CHAIN Solvent structure in particle interactions. Low pressure effects and analytic limits, 77684 Fifth virial coefficient for the Lennard-Jones fluid in two dimensions.Integral equation results, 8 12-21 CHARGE Vibrational spectrum of alkali metal cations in distorted solvation shells. A prediction, 1008-25 Reactions of carbon dioxide, carbon dioxide dimer, and water cations with various neutral molecules, 1084-92 Magnetooptical studies of liquid mixtures. Part 4. Additivity of the Faraday effect, the magnetic rotation dispersion constant, and the excess magnetic rotation in binary liquid mixtures, 1324-35 Charge-exchange mass spectra of ethyl acetate, methyl propionate, and propyl formate, 1450-7 Charge-exchange mass spectra of thiophene, pyrrole, and furan, 1516-22 CHEMI Reactions formine.electronicallv-excited free radicals. Part 2. Formation of nitrogen 4s. 2D. and 2P atoms in the harogen atom k difluoroamidogen reaction, and nitrogen atom Feactions, 1543-60 CHEMILUMINESCENCE Reactions forming electronically-excited free radicals. Part 2. Formation of nitrogen 4S, 2D, and 2P atoms in the hydrogen atom + difluoroamidogen reaction, and nitrogen atom reactions, 154360 CHLORIDE Vibrational spectra of matrix isolated aluminum chloride dimer. Isotopic fine structure and valence force field, 26-41 Optical properties of [M(L-L)2M(L-L)2Xd(ClO4)4, (M = platinum, palladium; L-L = 1,24iaminoeth-ane or 1,2diaminopropane; X = chlorine, bromine, iodine): bulk and small particles, 104-1 1 Photoelectron spectra of selenium dichloride and diselenium dichloride, 148-52 Photoelectron spectra and electronic structure of the transition metal dichlorides, MC4 (M = chromium, manganese, iron, cobalt, nickel), 506-1 9 Study of molecular motion in tert-butyl halides by pulsed proton magnetic resonance, 550-5 Halide ion induced quenching and enhancement of the fluorescence of fluoranthene solubilized in cetyltrimethylammonium bromide micelles, 685-92 Nuclear magnetic resonance spin-lattice relaxation and barriers in ethylenediammonium chloride, bromide, iodide, and sulfate, 1196-207 Quantum-resolved dynamics of excited states.Part 6. Radiative lifetime and collisional deactivation rates in bromine fluoride (B), 1569-85 CHLORINE Zeeman effect of chlorine nuclear quadrupole resonance and hydrogen bonding in 2,6-, 2,5-, and 3,5- dichlorophenols, 1055-60 Laser-induced fluorescence studies: the EX transition of chlorine. Part 5. Radiative lifetime of the B state, 1275-92 Reactions of chlorofluoromethylene radicals studied by laser-induced fluorescence, 1304-1 3 Laser-induced fluorescence studies: the B-X transition of chlorine. Part 6. Rotationallydependent predissociation, 1561-8 Quantum-resolved dynamics of excited states. Part 6. Radiative lifetime and collisional deactivation rates in bromine fluoride (B), 1569-85 J.C.S. FARADAY I1 SUBJECT INDEX VOL.76 (1980) CHLORO Electronic structure and valence ionization energies of trichlorooxochromium studied by ab initio and SW-Xu methods, 164-71 Infrared studies and thermodynamics of hydrogen bonding in 2-chloroethanol,3-chloropropanol and 4-chlorobutanol, 233-49 The 4A2, <-> 2Eg transitions in trans-dichlorobis(ethylenediamine)chromium( 1+) and trans- dichlorobis(1,3-diarninopropane)chromium(1+), 1381-7 CHLOROALC Infrared studies and thermodynamics of hydrogen bonding in 2-chloroethanol,3-chloropropanol and 4-chlorobutanol, 233-49 CHLOROBENZENE High resolution ultraviolet photoelectron spectra of monohalo- and pdihalobenzenes, 556-70 Thermodynamics of poly(dimethylsi1oxane) solutions, 895-904 CHLORODIFLUORO Nitric oxide and difluoromethylene fluorescence during vacuum ultraviolet photodissociation of chlorodifluoronitrosomethane, 1409-14 CHLORODIFLUORONITROSO Nitric oxide and difluoromethylene fluorescence during vacuum ultraviolet pho todissociation of chlorodifluoronitrosomethane, 1409-14 CHLORODIFLUORONITROSOMETHANE Nitric oxide and difluoromethylene fluorescence during vacuum ultraviolet photodissociation of chlorodifluoronitrosomethane, 1409-14 CHLOROFLUOROMETHANE Quantum-resolved dynamics of excited states.Part 6. Radiative lifetime and collisional deactivation rates in bromine fluoride (B), 1569-85 CHLOROFLUOROMETHYLENE Reactions of chlorofluoromethylene radicals studied by laser-induced fluorescence, 1304-1 3 CHLOROMETALLATE Resonance Raman, infrared, and electronic spectral studies of p-oxo-decahalodimetallate speciesosmium, rhenium, ruthenium, and tungsten, 1103-18 CHLOROMETHANE SCF-Xu study of the electronic structure of tetrahalomethanes, tetrahalosilanes, and tetrafluorogermane 1375-80 Magnetic birefringence in liquids of near-isotropic molecules, 1610-1 7 CHLORONITROSOMETHANE Photoelectron spectra of nitrosomethane, tert-nitrosobutane and some perhalonitrosomethanes, 844-59 CHLOROOXOCHROMIUM Electronic structure and valence ionization energies of trichlorooxochromium studied by ab initio and SW-Xu methods, 164-7 1 CHLOROPHENOL Zeeman effect of chlorine nuclear quadrupole resonance and hydrogen bonding in 2,6-, 2,5-, and 33- dichlorophenols, 1055-60 CHROMIUM Luminescence and 4A2+ 2E,2T1 absorption spectrum of hexaureachromium(II1) iodide and hexaureaalu- minum(II1) iodide :hexaureachromium(III), 82-7 Electronic structure and valence ionization energies of trichlorooxochromium studied by ab initio and SW-Xu methods, 164-71 Photoelectron spectra and electronic structure of the transition metal dichlorides, MC12 (M = chromium, manganese, iron, cobalt, nickel), 50619 Electronic structure and assignment of the ultraviolet photoelectron spectra of 6-methyl-2-0x0-pyridine complexes of dichromium(I1) and dimolybdenum(II), 885-94 Influence of the nonmagnetic cation upon the sign of the chromium(III)-chromium(III) coupling in trirutile compounds MCr206 (M = Te, W), 1224-33 The 4A2, <-> 2Eg transitions in trans-dichlorobis(ethylenediamine)chromium( 1+) and trans- dichlorobis(1,3-diaminopropane)chromiurn(1+), 138 1-7 CHROMOPHORE Influence of unsaturated chromophore excitation on the feasibility and selectivity of adjacent 0 bond cleavage, 1234-44 Attempted photoproduction of hydrogen using sulfophthalocyanines as chromophores for three- component systems, 1618-26 Calculations on the ground states of hydrogen cyanide monocation and hydrogen isocyanide monocatio- n, 319-23 Helium I and helium I1 photoelectron spectra of alkali fluorides in the vapor phase, 1523-32 Further study of the beryllium monohydride radical by UHF-type and configuration interaction methods, 1655-63 Study by high-temperature photoelectron spectroscopy of the electronic structure of the transition metal difluorides, cupric fluoride and zinc fluoride, 1672-82 J.C.S.FARADAY I1 SUBJECT INDEX VOL. 76 (1980) CLEAVAGE Influence of unsaturated chromophore excitation on the feasibility and selectivity of adjacent CT bond cleavage, 1234-44 CLUSTER Cluster model for solids, 520-33 Cluster groups, 534-41 CNDO Intramolecular hydrogen bond in ortho-hydroxyazobenzenes,827-33 COACERVATE Infrared investigation of water structure in desalination membranes, 136-47 COAGULATION Condensation modeling for highly supersaturated vapors: application to iron, 1494-5 1 5 COBALT Photoelectron spectra and electronic structure of the transition metal dichlorides, MC12 (M = chromium, manganese, iron, cobalt, nickel), 506-19 COLLISION Kinetics of excited states of bromine using laser excitation.Part 2. Radiative lifetime and collisional deactivation of the B3II(O+,) state, 405-19 Kinetic study of ground state atomic nitrogen, N(24S3.2), by timeresolved atomic resonance fluorescence 60619 A study of three dimol emissions of singlet oxygen, O,(lA.&), using a discharge flow shock tube, 1442-9 COLLOID Brownian dynamics of many-body systems, 1067-78 Statistical thermodynamics of fluid phase equilibrium in a conformal polydisperse system, 1458-67 Solvation forces in molecular fluids, 1478-84 COMPD Far infrared solution spectra. Volume of rotation and effective torque, 286301 Influence of the nonmagnetic cation upon the sign of the chromium(III)chromium(III) coupling in trirutile compounds MCrzOs (M = Te, W), 1224-33 Magnetooptical studies of liquid mixtures. Part 4.Additivity of the Faraday effect, the magnetic rotation dispersion constant, and the excess magnetic rotation in binary liquid mixtures, 1324-35 COMPUTER Non-Gaussian, non-Markov processes, 761-6 COND Transport properties in dilute gases: an approach using time-correlation functions. Part 1. Viscosity and thermal conductivity of gases and gas mixtures in which the exchange of molecular internal energy is slow, 735-46 Transport properties in dilute gases: an approach using time-correlation functions. Part 2. Viscosity and thermal conductivity of gases and gas mixtures in which the exchange of molecular internal energy is significant, 747-55 Study of the semiconductor-to-metal transition in vanadium dioxide and vanadium sesquioxide by ultraviolet photoelectron spectroscopy, 929-35 CONDENSATION Condensation modeling for highly supersaturated vapors: application to iron, 149&5 15 CONDON Energy disposal in the vacuum ultraviolet photodissociation of carbon disulfide and carbon diselenide, 905-14 CONFIGURATION Local configurations in cubic adamantane.Part 1,1586-91 CONFORMATION Dielectric study of the rotational equilibriums of succinonitrile, 197-204 Microwave spectrum and conformation of triformylmethane, 383-90 Viscosity dependent internal conversion in the rhodamine dye, Fast Acid Violet 2R, 1627-37 Internal conversion in the rhodamine dye, Fast Acid Violet 2R, 1638-45 CONFORMER Dielectric study of the rotational equilibriums of succinonitrile, 197-204 CONJUGATED Polynomial matrix method for the estimation of velectron energies of some linear conjugated molecules 1161-9 CONST Vibrational spectra of matrix isolated aluminum chloride dimer.Isotopic fine structure and valence force field, 2W1 Dielectric study of the rotational equilibriums of succinonitrile, 197-204 Halide ion induced quenching and enhancement of the fluorescence of fluoranthene solubilized in cetyltrimethylammonium bromide micelles, 685-92 Fifth virial coefficient for the Lennard-Jones fluid in two dimensions. Integral equation results, 8 12-21 Analysis of the vibrational spectrum of symmetrically solvated alkali metal cations, 979-1007 Prediction of phase equilibriums using the Redlich-Kwong equation of state, 1045-9 Resonance Raman, infrared, and electronic spectral studies of p-oxo-decahalodimetallate species J.C.S.FARADAY I1 SUBJECT INDEX VOL. 76 (1980) CONST(contd)osmium, rhenium, ruthenium, and tungsten, 1103-18 Evaluation of the van der Waals constant, internal pressure, and sound velocity in binary liquid mixtures from Flory’s theory, 12 15-18 Molecular structure of 1,2-dirnethyl-l,2tiazetidine.Electron diffraction and microwave study and normal coordinate analysis, 1293-303 CONVERSION Viscosity dependent internal conversion in the rhodamine dye, Fast Acid Violet 2R, 1627-37 Internal conversion in the rhodamine dye, Fast Acid Violet 2R, 163845 COORDINATE Vibrational spectra and normal coordinate analysis of silyl pseudohalides.Part 1. Silyl isothiocyanate, COPPER Contributions of orbital angular momentum to ligand hyperfine interactions in paramagnetic metal complexes, 660-6 Heat capacity of bis(adiponitrile)copper(I) nitrate. An order-disorder transition in a dilute system of nitrate ions, 803-1 1 Attempted photoproduction of hydrogen using sulfophthalocyanines as chromophores for three- component systems, 1618-26 Study by high-temperature photoelectron spectroscopy of the electronic structure of the transition metal difluorides, cupric fluoride and zinc fluoride, 1672-82 CORRELATION Nonlocal screening in a polar solvent, 67-8 1 Transport properties in dilute gases: an approach using time-correlation functions.Part 1. Viscosity and thermal conductivity of gases and gas mixtures in which the exchange of molecular internal energy is slow, 735-46 Transport properties in dilute gases: an approach using time-correlation functions. Part 2. Viscosity and thermal conductivity of gases and gas mixtures in which the exchange of molecular internal energy is significant, 747-5 5 Brownian dynamics of many-body systems, 1067-78 COTTON Molecular quadrupole moment of naphthalene, 1249-53 COUPLING Dynamic solvation. Ionic vibrations in nonstationary solvation shells, 1026-44 CRIT Fifth virial coefficient for the Lennard-Jones fluid in two dimensions.Integral equation results, 8 12-21 Prediction of phase equilibriums using the Redlich-Kwong equation of state, 1045-9 CROSS Kinetics and photochemistry of the nitrate radical. Part 1. Absolute absorption cross section, 785-93 CROSSING Source of anomalous fluorescence from solutions of 4‘-N,N’-dimethylaminobenzonitrilein polar solvents, 453-71 CRYSTAL Cluster groups, 534-41 Absorption, circular dichroism and magnetic circular dichroism spectra of trisodium praseodymium tris(oxydiacetate) di(sodium perchlorate) hexahydrate, 620-32 Influence of the nonmagnetic cation upon the sign of the chromium(III~hromium(III)coupling in trirutile compounds MCr206 (M = Te, W), 1224-33 Structure and dynamics of a new phase of anthracene, 1336-46 CTAB Halide ion induced quenching and enhancement of the fluorescence of fluoranthene solubilized in cetyltrimethylammonium bromide micelles, 68 5-92 CUBIC Local configurations in cubic adamantane.Part 1,158691 CUSP Cusped-Gaussian molecular wave functions. Part 3. Basis sets for the first-row atoms, 391-404 CYANIDE Calculations on the ground states of hydrogen cyanide monocation and hydrogen isocyanide monocatio- n. 319-23 Ionic and neutral optical emissions induced by helium(1a) excitation of nitriles, 1079-83 CYAN0 Emission spectra of the cations of cyanodiacetylene, methylcyanodiacetylene and ethylcyanodiacetylene in the gaseous phase. -A(n-1) +-X(d) band systems, 676-84 CYANOANTHRACENE External pressure effect on quenching of benaalanthracene and 9-cyanoanthracene fluorescence by dimethylmercury, 324-9 CYANOBIPHENYL Diffusion equation for the nematic phase dielectric loss, 21 7-20 J.C.S.FARADAY I1 SUBJECT INDEX VOL. 76 (1980) CY ANODIACETY LENE Emission spectra of the cations of cyanodiacetylene, methylcyanodiacetylene and ethylcyanodiacetylene in the gaseous phase. -A(d) +-X(d) band systems, 676-84 CYANOGEN Ionic and neutral optical emissions induced by helium(1ol) excitation of nitriles, 1079-83 CYANOINDOLINE Source of anomalous fluorescence from solutions of 4‘-N,N’4imethylaminobenzonitrilein polar solvents, 453-7 1 CYCLIZATION Kinetic matrix effects (response and density distribution functions): ring closure. Reaction of indolinobe-nzospiropyrans in glassy poly(alky1 methacrylates), 35 1-68 CY CLOHEXANE Thermodynamics of poly(dimethylsi1oxane) solutions, 895-904 DATA Study of self-association of tert-butyl alcohol by linear and nonlinear dielectric effects, 42-8 DEACTIVATION Kinetics of excited states of bromine using laser excitation.Part 2. Radiative lifetime and collisional deactivation of the B3n(O+,) state, 405-19 Laser-excitation studies of bromine. Collisional energy transfer involving resolved quantum states of excited Br2B3n(Ou+), 961-78 DECYL Ultrasonic relaxation of surfactants in water and deuterium oxide solutions, 794-802 DECYLTRIMETHYL Ultrasonic relaxation of surfactants in water and deuterium oxide solutions, 794-802 DECYLTRIMETHYLAMMONIUM Ultrasonic relaxation of surfactants in water and deuterium oxide solutions, 794-802 DENSITY Solvation forces in molecular fluids, 1478-84 DEPOLARIZATION Depolarized light scattering from gases of anisotropic molecules at intermediate pressures, 309-1 5 DEPOLARIZED Depolarized light scattering from gases of anisotropic molecules at intermediate pressures, 309-1 5 DER Evaluation of the van der Waals constant, internal pressure, and sound velocity in binary liquid mixtures from Flory’s theory, 1215-18 DESALINATION Infrared investigation of water structure in desalination membranes, 136-47 DETERGENCY Marangoni instability at a spherical interface.Breakdown of fluid drops at low surface tension and cytokinetic phenomena in the living cell, 1170-95 DEUTERIUM Kinetic study of the reactions of hydrogen and deuterium atoms with hydrogen bromide and deuterium bromide by timeresolved resonance fluorescence, 27685 DIAMINOALKANE Optical properties of [M(L-L)2M(L-L)2X2](ClO&, (M = platinum, palladium; L-L = 1,24aminoeth-ane or 1,2-diaminopropane; X = chlorine, bromine, iodine): bulk and small particles, 1041 1 DIAMINOPROPANE The 4A2g c-> 2Eg transitions in trans-dichlorobis(ethylenediamine)chromium( 1+) and trans- dichlorobis(1,3-diaminopropane)chromiurn(1+), 1381-7 DIATOMIC Hybrid potential function for bound diatomic molecules, 129-35 DIAZETIDINE Molecular structure of 1,2-dimethyl-l,24iazetidine.Electron diffraction and microwave study and normal coordinate analysis, 1293-303 DIBROMINE Kinetics of excited states of bromine using laser excitation.Part 2. Radiative lifetime and collisional deactivation of the B3lI(O+,) state, 405-19 DICHLORO Zeeman effect of chlorine nuclear quadrupole resonance and hydrogen bonding in 2,6-, 2,5-, and 3,5- dichlorophenols, 1055-60 DICHLOROPHENOL Zeeman effect of chlorine nuclear quadrupole resonance and hydrogen bonding in 2,6-, 2,5-, and 3,s dichlorophenols, 1055-60 DIELEC Study of self-association of tert-butyl alcohol by linear and nonlinear dielectric effects, 42-8 Static and dynamic Kerr-effect studies of glycerol in its highly viscous state, 112-21 Dielectric study of the rotational equilibriums of succinonitrile, 197-204 Viscous, viscoelastic and dielectric properties of a perfluorinated polymer, Krytox 143-AB, 205-16 Diffusion equation for the nematic phase dielectric loss, 217-20 J.C.S.FARADAY I1 SUBJECT INDEX VOL. 76 (1980) DIELEC(contd)Ion-pairing in aqueous media. An exact solution for the interaction energy associated with two dielectric spheres, 575-88 Dielectric relaxation studies in some phenolic Mannich bases, 589-97 Effect of electric fields on the far infrared absorption cross section of liquid aniline, 667-75 DIFFRACTION Molecular structure of 1,24imethyl-l,2-diazetidine.Electron diffraction and microwave study and normal coordinate analysis, 1293-303 DIFFUSION Diffusion equation for the nematic phase dielectric loss, 217-20 Light scattering study of the diffusion of interacting particles, 767-75 Brownian dynamics of many-body systems, 1067-78 Hard-sphere model of fused salts, 1347-53 DIFLUORIDE Reactions forming electronically-excited free radicals.Part 1. Ground-state reactions involving nitrogen mono- and difluoride, 71 1-28 DIFLUORO CH bond dipole, 172-6 DIFLUOROAMIDOGEN Reactions forming electronically-excited free radicals. Part 2. Formation of nitrogen 4S, 2D, and 2P atoms in the hydrogen atom + difluoroamidogen reaction, and nitrogen atom reactions, 1543-60 DIFLUOROMETHYLENE Nitric oxide and difluoromethylene fluorescence during vacuum ultraviolet photodissociation of chlorodifluoronitrosomethane, 1409-14 DIL Transport properties in dilute gases: an approach using timecorrelation functions.Part 1. Viscosity and thermal conductivity of gases and gas mixtures in which the exchange of molecular internal energy is slow, 735-46 Transport properties in dilute gases: an approach using time-correlation functions. Part 2. Viscosity and thermal conductivity of gases and gas mixtures in which the exchange of molecular internal energy is significant,747-55 DIMER Vibrational spectra of matrix isolated aluminum chloride dimer. Isotopic fine structure and valence force field, 2641 Reactions of carbon dioxide, carbon dioxide dimer, and water cations with various neutral molecules, 1084-92 DIMERIZATION Photodimerization of benzyl9-anthroate in the presence of triethylamine. Role of exciplex and triplet formation, 1-1 3 Reactions of chlorofluoromethylene radicals studied by laser-induced fluorescence, 1304-1 3 DIMETHYL Molecular structure of 1,2-dimethyl-l,24iazetidine.Electron diffraction and microwave study and normal coordinate analysis, 1293-303 DIMETHY LDIAZETIDINE Molecular structure of 1,24imethyl-l,24iaxtidine.Electron diffraction and microwave study and normal coordinate analysis, 1293-303 DIMOL A study of three dimol emissions of singlet oxygen, 02(lAg), using a discharge flow shock tube, 1442-9 DIOXANE Evaluation of the van der Waals constant, internal pressure, and sound velocity in binary liquid mixtures from Flory’s theory, 121 5-1 8 DIOXIDE Rate constants for the reactions of methylperoxy radicals with peroxy radicals, nitric oxide, and nitrogen dioxide using molecular modulation spectrometry, 1 53-63 Depolarized light scattering from gases of anisotropic molecules at intermediate pressures, 309-1 5 Atomization energies of the molecules LiSiO(g) and Si202(g) by mass spectrometric gaseous equilibriums 447-52 Reactions of carbon dioxide, carbon dioxide dimer, and water cations with various neutral molecules, 1084-92 DIPOLE CH bond dipole, 172-6 Dielectric study of the rotational equilibriums of succinonitrile, 197-204 Microwave spectrum and barrier to internal rotation of 2-methyl-2-nitropropane, 330-8 Microwave spectra of bromotrifluoromethane and iodotrifluoromethane.Structures and dipole moments 339-50 Microwave spectrum of acetyl isocyanate, 1208-1 3 DISCHARGE Vibrational relaxation of excited oxygen 02(lAg), studied with a discharge-flow-shock-tube technique,923-8 14 J.C.S.FARADAY I1 SUBJECT INDEX VOL. 76 (1980) DISELENIDE Energy disposal in the vacuum ultraviolet photodissociation of carbon disulfide and carbon diselenide, 905-14 DISILICON Atomization energies of the molecules LiSiO(g) and Si202(g) by mass spectrometric gaseous equilibriums 447-52 DISK Molecular dynamics simulation of a soft-disk system, 1646-54 DISORDER Absorption, circular dichroism and magnetic circular dichroism spectra of trisodium praseodymium tris(0xydiacetate) di(sodium perchlorate) hexahydrate, 620-32 Heat capacity of bis(adiponitrile)copper(I) nitrate. An order-disorder transition in a dilute system of nitrate ions, 803-1 1 Local configurations in cubic adamantane.Part 1, 1586-91 DISPERSION Analysis of the vibrational spectrum of symmetrically solvated alkali metal cations, 979-1007 Brownian dynamics of many-body systems, 1067-78 Statistical thermodynamics of fluid phase equilibrium in a conformal polydisperse system, 1458-67 DISPROPORTION ATION Reactions forming electronically-xcited free radicals. Part 1. Ground-state reactions involving nitrogen mone and difluoride, 71 1-28 DISSOCN Polarizable acid-water hydrogen bonds with aqueous solutions of carboxylic acids, 14-25 Atomization energies of complex gaseous yttrium carbides, 10 1-3 DISTORTION Vibrational spectrum of alkali metal cations in distorted solvation shells. A prediction, 1008-25 DISTRIBUTION Distribution of ions in electrolyte solutions and plasmas.Part 1, 1093-102 Theory of the electric double layer using a modified Poisson-Boltzmann equation, 1388408 Distribution of ions in electrolyte solutions and plasmas. Part 2, 1599-609 Molecular dynamics simulation of a soft-disk system, 1646-54 DISULFIDE Energy disposal in the vacuum ultraviolet photodissociation of carbon disulfide and carbon diselenide, 905-14 Energy transfer from state-selected photofragments. Electronic quenching of CS(A~II),VO_S, 91 5-22 Quadrupole moment and magnetic anisotropy of carbon disulfide, 1245-8 DITHIONITE Photochemistry of manganese porphyrins. Part 3. Interconversion of manganese(I1) and manganese(III), 1415-28 DMSO Analysis of the vibrational spectrum of symmetrically solvated alkali metal cations, 979-1007 DOPANT Mechanisms of singlet energy transfer in doped anthracene crystals at 5 K, studied by nanosecond spectrofluorimetry, 472-89 DOUBLE Thermodynamic approach to the interpretation of electrokinetic data near the isoelectric point, 1254-67 Theory of the electric double layer using a modified Poisson-Boltzmann equation, 1388-408 DRIVING Theory of transient response for arbitrarily strong driving fields, 542-9 DROP Marangoni instability at a spherical interface.Breakdown of fluid drops at low surface tension and cytokinetic phenomena in the living cell, 1170-95 DYE Viscosity dependent internal conversion in the rhodamine dye, Fast Acid Violet 2R, 1627-37 Internal conversion in the rhodamine dye, Fast Acid Violet 2R, 163845 DYNAMIC Dynamic solvation.Ionic vibrations in nonstationary solvation shells, 1026-44 DYNAMICS Non-Gaussian, non-Markov processes, 761-6 Brownian dynamics of many-body systems, 1067-78 Power reflection spectroscopy near the Brewster angle. Molecular dynamics of liquids, 1 147-60 Structure and dynamics of a new phase of anthracene, 1336-46 Molecular dynamics simulation of a soft-disk system, 1646-54 EARTH Vibrational structure in the luminescence spectra of uranium-doped tungstates with ordered perovskite structure, 872-84 ELEC Theory of transient response for arbitrarily strong driving fields, 542-9 Quadrupole moments of benzene, hexafluorobenzene and other nondipolar aromatic molecules, 648-59 J.C.S. FARADAY I1 SUBJECT INDEX VOL.76 (1980) ELEC(contd)Effect of electric fields on the far infrared absorption cross section of liquid aniline, 667-75 Zeeman effect of chlorine nuclear quadrupole resonance and hydrogen bonding in 2,&, 2,5-, and 3,5- dichlorophenols, 1055-60 Quadrupole moment and magnetic anisotropy of carbon disulfide, 1245-8 Molecular quadrupole moment of naphthalene, 1249-53 Theory of the electric double layer using a modified Poisson-Boltzmann equation, 1388408 ELECTROKINETIC Thermodynamic approach to the interpretation of electrokinetic data near the isoelectric point, 125467 ELECTROLYTE Ion-pairing in aqueous media. An exact solution for the interaction energy associated with two dielectric spheres, 575-88 Distribution of ions in electrolyte solutions and plasmas.Part 1, 1093-102 Theory of the electric double layer using a modified Poisson-Boltzmann equation, 1388-408 Distribution of ions in electrolyte solutions and plasmas. Part 2, 1599-609 ELECTRON Vibrational spectrum of alkali metal cations in distorted solvation shells. A prediction, 1008-25 Polynomial matrix method for the estimation of nAectron energies of some linear conjugated molecules 1161-9 Molecular structure of 1,2-dimethyl-l,24iazetidine.Electron diffraction and microwave study and normal coordinate analysis, 1293-303 ELECTRONIC Electronic structure and valence ionization energies of trichlorooxochromium studied by ab initio and SW-Xa methods, 164-7 1 Photoelectron spectra and electronic structure of the transition metal dichlorides, MCll (M = chromium, manganese, iron, cobalt, nickel), 506-1 9 Cluster model for solids, 520-33 Laser-excitation studies of bromine.Collisional energy transfer involving resolved quantum states of excited Br2B311(Oy+), 961-78 Resonance Raman, infrared, and electronic spectral studies of p-oxdecahalodimetallate species osmium, rhenium, ruthenium, and tungsten, 1103-18 Photoelectron spectra and valence shell electronic structure of zinc and cadmium difluoride, 13 14-23 SCF-Xa study of the electronic structure of tetrahalomethanes, tetrahalosilanes, and tetrafluorogermane 1375-80 Further study of the beryllium monohydride radical by UHF-type and configuration interaction methods, 1655-63 Study by high-temperature photoelectron spectroscopy of the electronic structure of the transition metal difluorides, cupric fluoride and zinc fluoride, 1672-82 ELECTROSTATIC Distribution of ions in electrolyte solutions and plasmas.Part 1, 1093-102 Theory of the electric double layer using a modified Poisson-Boltzmann equation, 1388-408 ELEMENT Cusped-Gaussian molecular wave functions. Part 3. Basis sets for the first-row atoms, 391-404 EMISSION Emission spectra of the cations of cyanodiacetylene, methylcyanodiacetylene and ethylcyanodiacetylene in the gaseous phase. -A(d) +X(n-1) band systems, 67684 A study of three dimol emissions of singlet oxygen, 02(lAg), using a discharge flow shock tube, 1442-9 EMULSION Light scattering study of the diffusion of interacting particles, 767-75 ENDOR Contributions of orbital angular momentum to ligand hyperfine interactions in paramagnetic metal complexes, 660-6 ENERGY Study of self-association of tert-butyl alcohol by linear and nonlinear dielectric effects, 42-8 Nonrigid molecules.Part 4. Hydrogen atom scrambling in the mass spectra of hydrocarbons, 88-95 Atomization energies of complex gaseous yttrium carbides, 10 1-3 Hybrid potential function for bound diatomic molecules, 129-35 Electronic structure and valence ionization energies of trichlorooxochromium studied by ab initio and SW-Xa methods, 16471 CH bond dipole, 172-6 Quantum-resolved dynamics of excited states. Part 5. The long-lived A311(lU) state of bromine, 177-96 Kinetic spectroscopy in the far vacuum ultraviolet. Part 5.Oscillator strengths for the 3s, 4s, 5s, 3d and 4d 4P~-2p3 4S03.2 transitions in atomic nitrogen, 369-82 SCF-Xa investigation of the ionization energies of perchlorate, sulfate, and phosphate anions, 441-5 Atomization energies of the molecules LiSiO(g) and Si202(g) by mass spectrometric gaseous equilibriums 447-52 Mechanisms of singlet energy transfer in doped anthracene crystals at 5 K, studied by nanosecond spectrofluorimetry, 472-89 Photoelectron spectra and electronic structure of the transition metal dichlorides, MCl2 (M = J.C.S. FARADAY I1 SUBJECT INDEX VOL. 76 (1980) ENERGY(contd)chromium, manganese, iron, cobalt, nickel), 506-1 9 Ion-pairing in aqueous media.An exact solution for the interaction energy associated with two dielectric spheres, 575-88 Lowest excited states of aza-analogs of stilbene. INDO/S calculation, 598-605 Emission spectra of the cations of cyanodiacetylene, methylcyanodiacetylene and ethylcyanodiacetylene in the gaseous phase. -A(d) +-X(d) band systems, 676-84 Transport properties in dilute gases: an approach using timecorrelation functions. Part 1. Viscosity and thermal conductivity of gases and gas mixtures in which the exchange of molecular internal energy is slow, 73546 Transport properties in dilute gases: an approach using time-correlation functions. Part 2. Viscosity and thermal conductivity of gases and gas mixtures in which the exchange of molecular internal energy is significant, 747-55 Magnetic susceptibility of expanded liquid selenium, 756-60 Intramolecular hydrogen bond in ortho-hydroxyazobenzenes, 827-33 Photoelectron spectra of nitrosomethane, tert-nitrosobutane and some perhalonitrosomethanes, 844-59 Energy disposal in the vacuum ultraviolet photodissociation of carbon disulfide and carbon diselenide, 905-14 Laser-excitation studies of bromine.Collisional energy transfer involving resolved quantum states of excited Br2B3II(OU+), 961-78 Analysis of the vibrational spectrum of symmetrically solvated alkali metal cations, 979-1007 Polynomial matrix method for the estimation of n-electron energies of some linear conjugated molecules 1161-9 Transition state model for water exchange in the first solvation shell of hydrated cations according to quantum chemical calculations, 1268-74 Vibrational energy transfer from carbon monoxide (v = l), nitrogen (v = 1) carbon dioxide(001), nitrous oxide(001), and carbonyl sulfide(001) to ozone, 1354-70 SCF-Xa study of the electronic structure of tetrahalomethanes, tetrahalosilanes, and tetrafluorogermane 1375-80 Laser-induced fluorescence studies: the EX transition of chlorine.Part 6. Rotationally-dependent predissociation, 1561-8 Local configurations in cubic adamantane. Part 1, 1586-91 Further study of the beryllium monohydride radical by UHF-type and configuration interaction methods, 165563 ENOL Electronic structure and assignment of the ultraviolet photoelectron spectra of 6-methyl-2-0x0-pyridine complexes of dichromium(I1) and dimolybdenum(II), 885-94 ENTROPY Study of self-association of tert-butyl alcohol by linear and nonlinear dielectric effects, 42-8 Dielectric study of the rotational equilibriums of succinonitrile, 197-204 Infrared studies and thermodynamics of hydrogen bonding in 2-chloroethanol,3-chloropropanol and 4-chlorobutanol, 233-49 Hard-sphere model of fused salts, 1347-53 EQUILPrediction of phase equilibriums using the Redlich-Kwong equation of state, 1045-9 Statistical thermodynamics of fluid phase equilibrium in a conformal polydisperse system, 1458-67 ESR Electron paramagnetic resonance and nuclear magnetic resonance studies of lipid-water systems, 96-1 00 Electron spin resonance studies of ion association.Part 8. Effects of ion-pairing on nitrogen-14 hyperfine splittings in psubstituted nitrobenzene anions, 822-6 Structure and fluxional behavior of the adducts of orthoquinones with organotin halides. An electron spin resonance study, 948-53 ESTER Charge-exchange mass spectra of ethyl acetate, methyl propionate, and propyl formate, 1450-7 ETHANOL Infrared studies and thermodynamics of hydrogen bonding in 2-chloroethanol,3-chloropropanol and 4-chlorobutanol, 23349 ETHER Positron lifetime study of the transition from glassy to normal liquid state for two phenyl ethers, 225-32 ETHYL Charge-exchange mass spectra of ethyl acetate, methyl propionate, and propyl formate, 1450-7 ETHYLAMINE Infrared studies of complexes between carboxylic acids and tertiary amines in argon matrixes, 834-43 ETHYLCYANODIACETYLENE Emission spectra of the cations of cyanodiacetylene, methylcyanodiacetylene and ethylcyanodiacetylene in the gaseous phase.-A(rl) +-X(n-l) band systems, 676-84 ETHYLENE Lowest excited states of aza-analogs of stilbene. INDO/S calculation, 598-605 Kinetic study of ground state atomic nitrogen, N(24S3.2), by time-resolved atomic resonance fluorescence J.C.S. FARADAY I1 SUBJECT INDEX VOL. 76 (1980) ETHY LENE(contd) 606-19 Reactions of carbon dioxide, carbon dioxide dimer, and water cations with various neutral molecules, 1084-92 ETHYLENEDIAMINE Carbon-1 3 and nitrogen-14 nuclear magnetic resonance study of triethylenediamine, 57 1-3 The 4A2, <-> 2E, transitions in trans-dichlorobis(ethylenediamine)chromium(1+ ) and trans- dichlorobis(1,3-diaminopropane)chrornium(1+), 138 1-7 ETHYLENEDIAMMONIUM Nuclear magnetic resonance spin-lattice relaxation and barriers in ethylenediammonium chloride, bromide, iodide, and sulfate, I 196-207 EXCHANGE On the NH proton tunneling rate in mese-tetraphenylporphine,729-3 1 Transport properties in dilute gases: an approach using time-correlation functions.Part 1. Viscosity and thermal conductivity of gases and gas mixtures in which the exchange of molecular internal energy is slow, 735-46 Transport properties in dilute gases: an approach using time-correlation functions. Part 2. Viscosity and thermal conductivity of gases and gas mixtures in which the exchange of molecular internal energy is significant, 747-55 Ultrasonic relaxation of surfactants in water and deuterium oxide solutions, 794-802 Influence of the nonmagnetic cation upon the sign of the chromium(III~hromium(II1)coupling in trirutile compounds MCr206 (M = Te, W), 1224-33 Transition state model for water exchange in the first solvation shell of hydrated cations according to quantum chemical calculations, 1268-74 Charge-exchange mass spectra of ethyl acetate, methyl propionate, and propyl formate, 1450-7 Charge-exchange mass spectra of thiophene, pyrrole, and furan, 151 6-22 EXCIMER Photodimerization of benzyl9-anthroate in the presence of triethylamine.Role of exciplex and triplet formation, 1-1 3 EXCIPLEX External pressure effect on quenching of benz[a]anthracene and 9-cyanoanthracene fluorescence by dimethylmercury, 324-9 Source of anomalous fluorescence from solutions of 4'-N,N'-dimethylaminobenzonitrile in polar solvents, 453-7 1 EXCITATION Kinetics of excited states of bromine using laser excitation.Part 2. Radiative lifetime and collisional deactivation of the B3lT(O+,) state, 405-19 Vibrational relaxation of excited oxygen 02(lAg), studied with a discharge-flow-shock-tube technique,923-8 Laser-excitation studies of bromine. Collisional energy transfer involving resolved quantum states of excited Br2B3n(OU+), 961-78 Ionic and neutral optical emissions induced by helium(1a) excitation of nitriles, 1079-83 Resonance Raman, infrared, and electronic spectral studies of p-oxo-decahalodimetallatespeciesosmium, rhenium, ruthenium, and tungsten, 1103-18 Theory of the kinetic isotope effect in proton transfer reactions in a polar medium, 1128-46 Influence of unsaturated chromophore excitation on the feasibility and selectivity of adjacent Q bond cleavage, 1234-44 A study of three dimol emissions of singlet oxygen, 02(lAg), using a discharge flow shock tube, 1442-9 EXCITED Kinetics of excited states of bromine using laser excitation.Part 2. Radiative lifetime and collisional deactivation of the B3lT(O+,) state, 405-19 Vibrational relaxation of excited oxygen 02(lA,), studied with a discharge-flow-shock-tube technique,923-8 Laser-excitation studies of bromine. Collisional energy transfer involving resolved quantum states of excited Br2B3n(Ou+), 961-78 EXHAUST Condensation modeling for highly supersaturated vapors: application to iron, 1494-5 15 EXTERNAL Vibrational spectrum of alkali metal cations in distorted solvation shells.A prediction, 1008-25 FAR Kinetic spectroscopy in the far vacuum ultraviolet. Part 5. Oscillator strengths for the 3s, 4s, 5s, 3d and 4d 4PJ-2p3 4S03.2 transitions in atomic nitrogen, 369-82 FILM Thinning and rupture of ring-shaped films, 25&66 Electronic transitions at the surface of potassium iodide microcrystals. Part 1. Surface states, 420-30 FLAME Condensation modeling for highly supersaturated vapors: application to iron, 1494-5 1 5 FLOW Vibrational relaxation of excited oxygen 02(lA&, studied with a discharge-flow-shock-tube technique, 18 J.C.S. FARADAY I1 SUBJECT INDEX VOL.76 (1980) FLOW(contd)923-8 FLUID Solvent structure in particle interactions. Low pressure effects and analytic limits, 776-84 Fifth virial coefficient for the Lennard-Jones fluid in two dimensions. Integral equation results, 8 12-21 Marangoni instability at a spherical interface. Breakdown of fluid drops at low surface tension and cytokinetic phenomena in the living cell, 1170-95 Solvation forces in molecular fluids, 1478-84 Molecular dynamics simulation of a soft-disk system, 1646-54 FLUORANTHENE Halide ion induced quenching and enhancement of the fluorescence of fluoranthene solubilized in cetyltrimethylammonium bromide micelles, 685-92 FLUORESCENCE Laser-induced fluorescence of iodine monobromide: the Bm(O +) excited state, 49-66 Quantum-resolved dynamics of excited states.Part 5. The long-lived A3n( I,) state of bromine, 177-96 Kinetic study of the reactions of hydrogen and deuterium atoms with hydrogen bromide and deuterium bromide by time-resolved resonance fluorescence, 276-85 External pressure effect on quenching of benz[a]anthracene and 9-cyanoanthracene fluorescence by dimethylmercury, 324-9 Kinetics of excited states of bromine using laser excitation. Part 2. Radiative lifetime and collisional deactivation of the BVI(O+,) state, 405-19 Source of anomalous fluorescence from solutions of 4'-N,N'-dimethylaminobenzonitrile in polar solvents, 453-71 Mechanisms of singlet energy transfer in doped anthracene crystals at 5 K, studied by nanosecond spectrofluorimetry, 472-89 Lowest excited states of aza-analogs of stilbene. INDO/S calculation, 598-605 Kinetic study of ground state atomic nitrogen, N(24S3.2), by time-resolved atomic resonance fluorescence 606-19 Halide ion induced quenching and enhancement of the fluorescence of fluoranthene solubilized in cetyltrimethylammonium bromide micelles, 68 5-92 Reactions forming electronically-excited free radicals.Part 1. Ground-state reactions involving nitrogen mono- and difluoride, 71 1-28 Energy transfer from state-selected photofragments. Electronic quenching of CS(Aln),-w5,9 15-22 Ionic and neutral optical emissions induced by helium(1cr) excitation of nitriles, 1079-83 Laser-induced fluorescence studies: the B-X transition of chlorine.Part 5. Radiative lifetime of the B state, 1275-92 Reactions of chlorofluoromethylene radicals studied by laser-induced fluorescence, 1 304-1 3 Vibrational energy transfer from carbon monoxide (v = l), nitrogen (v = 1) carbon dioxide(001), nitrous oxide(001), and carbonyl sulfide(001) to ozone, 1354-70 Nitric oxide and difluoromethylene fluorescence during vacuum ultraviolet photodissociation of chlorodifluoronitrosomethane, 1409-14 Laser-induced fluorescence studies: the B-X transition of chlorine. Part 6. Rotationally-dependent predissociation, 1561-8 Quantum-resolved dynamics of excited states. Part 6. Radiative lifetime and collisional deactivation rates in bromine fluoride (B), 1569-85 Attempted photoproduction of hydrogen using sulfophthalocyanines as chromophores for three- component systems, 1618-26 Viscosity dependent internal conversion in the rhodamine dye, Fast Acid Violet 2R, 1627-37 Indolyl alkali metal ion pairs in the excited state.Part 3. Solvent-excited solute relaxation in the S1-and TI-states, 1664-71 FLUORIDE Halide ion induced quenching and enhancement of the fluorescence of fluoranthene solubilized in cetyltrimethylammonium bromide micelles, 685-92 Reactions forming electronically-excited free radicals. Part 1. Ground-state reactions involving nitrogen mono- and difluoride, 71 1-28 Photoelectron spectra and valence shell electronic structure of zinc and cadmium difluoride, 13 14-23 SCF-Xa study of the electronic structure of tetrahalomethanes, tetrahalosilanes, and tetrafluorogermane 1375-80 Helium I and helium I1 photoelectron spectra of alkali fluorides in the vapor phase, 1523-32 Quantum-resolved dynamics of excited states. Part 6.Radiative lifetime and collisional deactivation rates in bromine fluoride (B), 1569-85 Study by high-temperature photoelectron spectroscopy of the electronic structure of the transition metal difluorides, cupric fluoride and zinc fluoride, 1672-82 FLUORINE Cusped-Gaussian molecular wave functions. Part 3. Basis sets for the first-row atoms, 391-404 FLUORO Polarizable acid-water hydrogen bonds with aqueous solutions of carboxylic acids, 14-25 Viscous, viscoelastic and dielectric properties of a perfluorinated polymer, Krytox 143-AB, 205-1 6 J.C.S.FARADAY I1 SUBJECT INDEX VOL. 76 (1980) FLUOROACETIC Polarizable acid-water hydrogen bonds with aqueous solutions of carboxylic acids, 14-25 Infrared studies of complexes between carboxylic acids and tertiary amines in argon matrixes, 834-43 FLUOROAMIDOGEN Reactions forming electronically-excited free radicals. Part 2. Formation of nitrogen 4S, 2D, and 2P atoms in the hydrogen atom + difluoroamidogen reaction, and nitrogen atom reactions, 1543-60 FLUOROBENZENE Quadrupole moments of benzene, hexafluorobenzene and other nondipolar aromatic molecules, 648-59 FLUOROBENZONITRILE Ionic and neutral optical emissions induced by helium(1a) excitation of nitriles, 1079-83 FLUOROIMIDOGEN Reactions forming electronically-excited free radicals.Part 2. Formation of nitrogen 4S, 2D, and 2P atoms in the hydrogen atom + difluoroamidogen reaction, and nitrogen atom reactions, 1543-60 FLUOROMETHANE CH bond dipole, 172-6 SCF-Xa study of the electronic structure of tetrahalomethanes, tetrahalosilanes, and tetrafluorogermane 137580 FLUORONITROSOMETHANE Photoelectron spectra of nitrosomethane, tert-nitrosobutane and some perhalonitrosomethanes, 844-59 FLUOROOCTANOATE Ultrasonic relaxation of surfactants in water and deuterium oxide solutions, 794-802 FLUROIDE Helium I and helium I1 photoelectron spectra of alkali fluorides in the vapor phase, 1523-32 FLUXION Structure and fluxional behavior of the adducts of orthoquinones with organotin halides.An electron spin resonance study, 948-53 FOKKER Non-Gaussian, non-Markov processes, 761-6 FORCE Vibrational spectra of matrix isolated aluminum chloride dimer. Isotopic fine structure and valence force field, 2W1 Vibrational spectra and normal coordinate analysis of silyl pseudohalides. Part 1. Silyl isothiocyanate, 496505 Role of intermolecular forces in proton-transfer reactions, 954-60 Analysis of the vibrational spectrum of symmetrically solvated alkali metal cations, 979-1007 Resonance Raman, infrared, and electronic spectral studies of p-oxcdecahalodimetallate speciesosmium, rhenium, ruthenium, and tungsten, 1103-18 Molecular structure of 1,2-dimethy1-1,2-diazetidine. Electron diffraction and microwave study and normal coordinate analysis, 1293-303 Statistical thermodynamics of fluid phase equilibrium in a conformal polydisperse system, 1458-67 Solvation forces in molecular fluids, 1478-84 FORMATE Charge-exchange mass spectra of ethyl acetate, methyl propionate, and propyl formate, 1450-7 FORMATION Photodimerization of benzyl9-anthroate in the presence of triethylamine.Role of exciplex and triplet formation, 1-1 3 Atomization energies of complex gaseous yttrium carbides, 101-3 Atomization energies of the molecules LiSiO(g) and Si202(g) by mass spectrometric gaseous equilibriums 447-52 FORMIC Polarizable acid-water hydrogen bonds with aqueous solutions of carboxylic acids, 14-25 FORMYLMETHANE Microwave spectrum and conformation of triformylmethane, 383-90 FRAGMENTATION Nonrigid molecules. Part 4.Hydrogen atom scrambling in the mass spectra of hydrocarbons, 88-95 FRANCK Energy disposal in the vacuum ultraviolet photodissociation of carbon disulfide and carbon diselenide, 905- 14 FREE Study of self-association of tert-butyl alcohol by linear and nonlinear dielectric effects, 42-8 Atomization energies of complex gaseous yttrium carbides, 101-3 Atomization energies of the molecules LiSiO(g) and Si202(g) by mass spectrometric gaseous equilibriums 447-52 Local configurations in cubic adamantane. Part 1, 158691 FRICTION Effect of electric fields on the far infrared absorption cross section of liquid aniline, 667-75 FUNCTION Nonlocal screening in a polar solvent, 67-8 1 Atomization energies of complex gaseous yttrium carbides, 101-3 J.C.S.FARADAY fI SUBJECT INDEX VOL. 76 (1980) FUNCTION(contd)Cusped-Gaussian molecular wave functions. Part 3. Basis sets for the first-row atoms, 39 1-404 Transport properties in dilute gases: an approach using time-correlation functions. Part 1. Viscosity and thermal conductivity of gases and gas mixtures in which the exchange of molecular internal energy is slow, 73546 Transport properties in dilute gases: an approach using time-correlation functions. Part 2. Viscosity and thermal conductivity of gases and gas mixtures in which the exchange of molecular internal energy is significant, 747-55 Brownian dynamics of many-body systems, 1067-78 Theory of the electric double layer using a modified Poisson-Boltzmann equation, 1388-408 Molecular dynamics simulation of a soft-disk system, 1646-54 FURAN Charge-exchange mass spectra of thiophene, pyrrole, and furan, 1516-22 FUSED Hard-sphere model of fused salts, 1347-53 GAUSSIAN Cusped-Gaussian molecular wave functions.Part 3. Basis sets for the first-row atoms, 391-404 Non-Gaussian, non-Markov processes, 761-6 GEOMETRY Statistical geometry of hard-sphere systems, 693-703 GLASS Infrared investigation of water structure in desalination membranes, 13647 Positron lifetime study of the transition from glassy to normal liquid state for two phenyl ethers, 225-32 Volume relaxation in simple liquids, 704-10 GLYCEROL Static and dynamic Kerr-effect studies of glycerol in its highly viscous state, 112-21 GLYCOL Internal conversion in the rhodamine dye, Fast Acid Violet 2R, 1638-45 GRADIENT Zeeman effect of chlorine nuclear quadrupole resonance and hydrogen bonding in 2,6-, 2,5-, and 33- dichlorophenols, 1055-60 GROUP Cluster groups, 534-41 SCF-Xa study of the electronic structure of tetrahalomethanes, tetrahalosilanes, and tetrafluorogermane 1375-80 GROWTH Condensation modeling for highly supersaturated vapors: application to iron, 1494-5 15 HALIDE Optical properties of [M(L-L)2M(L-L)2X,](C104)4, (M = platinum, palladium; L-L = 1,2-diaminoeth-ane or 1,24iaminopropane; X = chlorine, bromine, iodine): bulk and small particles, 104-1 1 Far infrared solution spectra.Volume of rotation and effective torque, 286-301 Study of molecular motion in tert-butyl halides by pulsed proton magnetic resonance, 55&5 Halide ion induced quenching and enhancement of the fluorescence of fluoranthene solubilized in cetyltrimethylammonium bromide micelles, 68592 Structure and fluxional behavior of the adducts of orthoquinones with organotin halides.An electron spin resonance study, 948-53 Nuclear magnetic resonance spin-lattice relaxation and barriers in ethylenediammonium chloride, bromide, iodide, and sulfate, 1 196-207 Hard-sphere model of fused salts, 1347-53 HALO High resolution ultraviolet photoelectron spectra of monohalo- and p-dihalobenzenes, 55670 HALOBENZENE High resolution ultraviolet photoelectron spectra of monohale and pdihalobenzenes, 55670 HALOMETHANE SCF-Xa study of the electronic structure of tetrahalomethanes, tetrahalosilanes, and tetrafluorogermane 1375-80 HALONITROSOMETHANE Photoelectron spectra of nitrosomethane, tert-nitrosobutane and some perhalonitrosomethanes, 844-59 HALOORGANO Structure and fluxional behavior of the adducts of orthoquinones with organotin halides.An electron spin resonance study, 948-53 HALOORGANOTIN Structure and fluxional behavior of the adducts of orthoquinones with organotin halides. An electron spin resonance study, 948-53 HALOTRIFLUORO Microwave spectra of bromotrifluoromethane and iodotrifluoromethane. Structures and dipole moments 339-50 HALOTRIFLUOROMETHANE Microwave spectra of bromotrifluoromethane and iodotrifluoromethane.Structures and dipole moments J.C.S. FARADAY I1 SUBJECT INDEX VOL. 76 (1980) HALOTRIFLUOROMETHANE(contd)339-50 HARD Statistical geometry of hard-sphere systems, 693-703 Hard-sphere model of fused salts, 1347-53 HEAT Study of self-association of tert-butyl alcohol by linear and nonlinear dielectric effects, 42-8 Atomization energies of complex gaseous yttrium carbides, 101-3 Dielectric study of the rotational equilibriums of succinonitrile, 197-204 Infrared studies and thermodynamics of hydrogen bonding in 2-chloroethanol,3-chloropropanoland 4-chlorobutanol, 233-49 Atomization energies of the molecules LiSiO(g) and Si202(g) by mass spectrometric gaseous equilibriums 47-52 Heat capacity of bis(adiponitrile)copper(I)nitrate.An order-disorder transition in a dilute system of nitrate ions, 803-1 1 Hard-sphere model of fused salts, 1347-53 HEATING Vibrational relaxation of excited oxygen 02(lAg), studied with a discharge-flow-shock-tube technique,923-8 HEPTYL Diffusion equation for the nematic phase dielectric loss, 217-20 HEPTYLCYANO Diffusion equation for the nematic phase dielectric loss, 21 7-20 HEPTY LCY ANOBIPHENY L Diffusion equation for the nematic phase dielectric loss, 217-20 HETEROCYCLE Far infrared solution spectra. Volume of rotation and effective torque, 286-301 Charge-exchange mass spectra of thiophene, pyrrole, and furan, 15 16-22 HYDRATE Absorption, circular dichroism and magnetic circular dichroism spectra of trisodium praseodymium tris(oxydiacetate) di(sodium perchlorate) hexahydrate, 62&32 Contributions of orbital angular momentum to ligand hyperfine interactions in paramagnetic metal complexes, 66&6 HYDRATION Study of solvation models.Interpretation of solvent effect on the 7c* <-n transition of methyl acetate, 490-5 Transition state model for water exchange in the first solvation shell of hydrated cations according to quantum chemical calculations, 1268-74 HYDRIDE Further study of the beryllium monohydride radical by UHF-type and configuration interaction methods, 1655-63 HYDROCARBON Nonrigid molecules. Part 4. Hydrogen atom scrambling in the mass spectra of hydrocarbons, 88-95 Multipole analysis of MNDO results, 302-8 HYDROGEN Polarizable acid-water hydrogen bonds with aqueous solutions of carboxylic acids, 14-25 Nonrigid molecules.Part 4. Hydrogen atom scrambling in the mass spectra of hydrocarbons, 88-95 CH bond dipole, 172-6 Infrared studies and thermodynamics of hydrogen bonding in 2-chloroethanol,3-chloropropanol and 4-chlorobutanol, 233-49 Kinetic study of the reactions of hydrogen and deuterium atoms with hydrogen bromide and deuterium bromide by time-resolved resonance fluorescence, 27685 Calculations on the ground states of hydrogen cyanide monocation and hydrogen isocyanide monocatio- n, 3 19-23 Dielectric relaxation studies in some phenolic Mannich bases, 589-97 Reactions forming electronically-excited free radicals. Part 1. Ground-state reactions involving nitrogen mone and difluoride, 71 1-28 Intramolecular hydrogen bond in orthwhydroxyazobenzenes,827-33 Zeeman effect of chlorine nuclear quadrupole resonance and hydrogen bonding in 2,&, 2,5-, and 3,5- dichlorophenols, 1055-60 Influence of screening of intramolecular easily polarizable hydrogen bonds on their infrared absorbance, 1061-6 Reactions of carbon dioxide, carbon dioxide dimer, and water cations with various neutral molecules, 1084-92 Reactions forming electronically-excited free radicals. Part 2.Formation of nitrogen 4S, 2D, and 2P atoms in the hydrogen atom + difluoroamidogen reaction, and nitrogen atom reactions, 1543-60 Quantum-resolved dynamics of excited states. Part 6. Radiative lifetime and collisional deactivation rates in bromine fluoride (B), 1569-85 Attempted photoproduction of hydrogen using sulfophthalocyanines as chromophores for three- J.C.S.FARADAY I1 SUBJECT INDEX VOL. 76 (1980) HYDROGEN(contd)component systems, 161 8-26 HYDROPEROXY Rate constants for the reactions of methylperoxy radicals with peroxy radicals, nitric oxide, and nitrogen dioxide using molecular modulation spectrometry, 1 53-63 HYDROQUINOLINESource of anomalous fluorescence from solutions of 4'-N,N'4imethylaminobenzonitrile in polar solvents, 453-71 HYDROXYAZOBENZENE Intramolecular hydrogen bond in ortho-hydroxyazobenzenes,827-33 HYDROXYHEXADECANOIC Theory of cooperative phenomena in monolayers of hydroxyhexadecanoic acid isomers, 43 1-40 HYDROXYPYRIDINE Electronic structure and assignment of the ultraviolet photoelectron spectra of 6-methyl-2-0x0-pyridine complexes of dichromium(I1) and dimolybdenum(II), 885-94 HYPERFINE Further study of the beryllium monohydride radical by UHF-type and configuration interaction methods, 1655-63 HYPERNETTED Solvent structure in particle interactions.Low pressure effects and analytic limits, 77684 Fifth virial coefficient for the Lennard-Jones fluid in two dimensions. Integral equation results, 812-21 IMMISCIBILITY Prediction of phase equilibriums using the Redlich-Kwong equation of state, 1045-9 INDO Lowest excited states of aza-analogs of stilbene. INDO/S calculation, 598-605 INDOLINE Source of anomalous fluorescence from solutions of 4'-N,Ndimethylaminobenzonitrile in polar solvents, 453-71 INDOLINOBENZOSPIRAN Kinetic matrix effects (response and density distribution functions): ring closure.Reaction of indolinobe- nzospiropyrans in glassy poly(alky1 methacrylates), 35 1-68 INDOLYL Indolyl alkali metal ion pairs in the excited state. Part 3. Solvent-excited solute relaxation in the S1-and TI-states, 16647 1 INDUCED Kinetics of excited states of bromine using laser excitation. Part 2. Radiative lifetime and collisional deactivation of the BTI(O+,) state, 405-19 INERT Laser-excitation studies of bromine. Collisional energy transfer involving resolved quantum states of excited Br2B3II(OU+), 961-78 INSTABILITY Marangoni instability at a spherical interface. Breakdown of fluid drops at low surface tension and cytokinetic phenomena in the living cell, 1170-95 INTERACTION Ion-pairing in aqueous media.An exact solution for the interaction energy associated with two dielectric spheres, 575-88 Contributions of orbital angular momentum to ligand hyperfine interactions in paramagnetic metal complexes, 660-6 Solvent structure in particle interactions. Low pressure effects and analytic limits, 776-84 Dynamic solvation. Ionic vibrations in nonstationary solvation shells, 1026-44 INTERFACE Thinning and rupture of ring-shaped films, 250-66 Solvation forces in molecular fluids, 1478-84 INTERFACIAL Marangoni instability at a spherical interface. Breakdown of fluid drops at low surface tension and cytokinetic phenomena in the living cell, 1170-95 INTERION Distribution of ions in electrolyte solutions and plasmas. Part 1, 1093-102 INTERMOL Role of intermolecular forces in proton-transfer reactions, 954-60 INTERNAL Nonrigid molecules.Part 4. Hydrogen atom scrambling in the mass spectra of hydrocarbons, 88-95 Evaluation of the van der Waals constant, internal pressure, and sound velocity in binary liquid mixtures from Flory's theory, 12 1 5-18 Viscosity dependent internal conversion in the rhodamine dye, Fast Acid Violet 2R, 1627-37 Internal conversion in the rhodamine dye, Fast Acid Violet 2R, 1638-45 INTERPARTICLE Statistical thermodynamics of fluid phase equilibrium in a conformal polydisperse system, 1458-67 J.C.S. FARADAY I1 SUBJECT INDEX VOL. 76 (1980) INTERSYSTEM Source of anomalous fluorescence from solutions of 4'-N,N'-dirnethylaminobenzonitrile in polar solvents, 453-71 INTRAMOL Influence of screening of intramolecular easily polarizable hydrogen bonds on their infrared absorbance, 1061-6 INVERSION Dielectric study of the rotational equilibriums of succinonitrile, 197-204 IODIDE Luminescence and 4A+ 2E,2T1 absorption spectrum of hexaureachromium(II1) iodide and hexaureaalu- minum(II1) iodide :hexaureachromium(III), 82-7 Optical properties of [M(L-L)2M(L-L)2X2](ClO&, (M = platinum, palladium; L-L = lY2-diaminoeth-ane or lY2-diaminopropane; X = chlorine, bromine, iodine): bulk and small particles, 104-1 1 Electronic transitions at the surface of potassium iodide microcrystals.Part 1.Surface states, 420-30 Study of molecular motion in tert-butyl halides by pulsed proton magnetic resonance, 550-5 Halide ion induced quenching and enhancement of the fluorescence of fluoranthene solubilized in cetyltrimethylammonium bromide micelles, 68 5-92 Nuclear magnetic resonance spin-lattice relaxation and barriers in ethylenediammonium chloride, bromide, iodide, and sulfate, 1196-207 IODINE Laser-induced fluorescence of iodine monobromide: the Bm(O +) excited state, 49-66 IODOBENZENE High resolution ultraviolet photoelectron spectra of monohalo- and pdihalobenzenes, 556-70 IODOMETHANE Evaluation of the van der Waals constant, internal pressure, and sound velocity in binary liquid mixtures from Flory's theory, 1215-18 SCF-Xa study of the electronic structure of tetrahalomethanes, tetrahalosilanes, and tetrafluorogermane 1375-80 IODOTRIFLUOROMETHANE Microwave spectra of bromotrifluoromethane and iodotrifluoromethane. Structures and dipole moments 339-50 ION Nonrigid molecules. Part 4.Hydrogen atom scrambling in the mass spectra of hydrocarbons, 88-95 Ion-pairing in aqueous media. An exact solution for the interaction energy associated with two dielectric spheres, 575-88 Electron spin resonance studies of ion association. Part 8. Effects of ion-pairing on nitrogen-14 hyperline splittings in psubstituted nitrobenzene anions, 822-6 Dynamic solvation. Ionic vibrations in nonstationary solvation shells, 1026-44 Reactionsof carbon dioxide, carbon dioxide dimer, and water cations with various neutral molecules, 1084-92 Distribution of ions in electrolyte solutions and plasmas. Part 1, 1093-102 Distribution of ions in electrolyte solutions and plasmas. Part 2, 1599-609 Indolyl alkali metal ion pairs in the excited state.Part 3. Solvent-excited solute relaxation in the S1- and TI-states, 1664-7 1 IONIC Thermodynamic approach to the interpretation of electrokinetic data near the isoelectric point, 1254-67 IONIZATION Electronic structure and valence ionization energies of trichlorooxochromium studied by ab initio and SW-Xa methods, 164-71 SCF-Xa investigation of the ionization energies of perchlorate, sulfate, and phosphate anions, 441-5 Atomization energies of the molecules LiSiO(g) and Si202(g) by mass spectrometric gaseous equilibriums 447-52 Photoelectron spectra and electronic structure of the transition metal dichlorides, MC4 (M = chromium, manganese, iron, cobalt, nickel), 506-19 Emission spectra of the cations of cyanodiacetylene, methylcyanodiacetylene and ethylcyanodiacetylene in the gaseous phase.-A(.n-1) +-X(rl) band systems, 67684 Photoelectron spectra of nitrosomethane, tert-nitrosobutane and some perhalonitrosomethanes, 844-59 SCF-Xa study of the electronic structure of tetrahalomethanes, tetrahalosilanes, and tetrafluorogermane 1375-80 Nitric oxide and difluoromethylene fluorescence during vacuum ultraviolet photodissociation of chlorodifluoronitrosomethane, 1409-14 Some model potentials for the ammoniated electron, 1592-8 IR Polarizable acid-water hydrogen bonds with aqueous solutions of carboxylic acids, 14-25 Vibrational spectra of matrix isolated aluminum chloride dimer.Isotopic fine structure and valence force field, 26-41 Infrared investigation of water structure in desalination membranes, 1 36-47 Infrared studies and thermodynamics of hydrogen bonding in 2-chloroethano1, hhloropropanol and 4-chlorobutanol, 233-49 24 J.C.S. FARADAY I1 SUBJECT INDEX VOL. 76 (1980) IR(contd)Far infrared solution wectra. Volume of rotation and effective toraue. 286301 Vibrational spectra ana normal coordinate analysis of silyl pseudohalides. Part 1. Silyl isothiocyanate, 496-505 Effect of electric fields on the far infrared absorption cross section of liquid aniline, 667-75 Infrared studies of complexes between carboxylic acids and tertiary amines in argon matrixes, 834-43 Low-frequency bending motions of the silyl pseudohalides SiH3NCY (Y = 0,S, Se).An experimental and theoretical study, 860-71 Influence of screening of intramolecular easily polarizable hydrogen bonds on their infrared absorbance, 1061-6 Power reflection spectroscopy near the Brewster angle. Molecular dynamics of liquids, 1147-60 Molecular structure of 1,2-dimethy1-1,2-diazetidine. Electron diffraction and microwave study and normal coordinate analysis, 1293-303 Vibrational energy transfer from carbon monoxide (v = l), nitrogen (v = 1) carbon dioxide(001), nitrous oxide(001), and carbonyl sulfide(001) to ozone, 1354-70 Attempted photoproduction of hydrogen using sulfophthalocyanines as chromophores for three- component systems, 1618-26 IRON Photoelectron spectra and electronic structure of the transition metal dichlorides, MC12 (M = chromium, manganese, iron, cobalt, nickel), 506-1 9 Condensation modeling for highly supersaturated vapors: application to iron, 1494-5 15 IRRADN Photodimerization of benzyl9-anthroate in the presence of triethylamine.Role of exciplex and triplet formation, 1-13 ISOCYANATE Microwave spectrum of acetyl isocyanate, 1208-13 ISOCYANIDE Calculations on the ground states of hydrogen cyanide monocation and hydrogen isocyanide monocatio- n. 319-23 ISOELEC Thermodynamic approach to the interpretation of electrokinetic data near the isoelectric point, 125467 ISOMERIC Charge-exchange mass spectra of ethyl acetate, methyl propionate, and propyl formate, 1450-7 ISOTHIOCYANATE Vibrational spectra and normal coordinate analysis of silyl pseudohalides.Part 1. Silyl isothiocyanate, 496505 ISOTOPE Role of intermolecular forces in proton-transfer reactions, 954-60 Theory of the kinetic isotope effect in proton transfer reactions in a polar medium, 1128-46 IVA SCF-Xa study of the electronic structure of tetrahalomethanes, tetrahalosilanes, and tetrafluorogermane 1375-80 JONES Solvent structure in particle interactions. Low pressure effects and analytic limits, 776-84 Fifth virial coefficient for the Lennard-Jones fluid in two dimensions. Integral equation results, 812-21 KERR Static and dynamic Kerr-effect studies of glycerol in its highly viscous state, 1 12-2 1 Theory of transient response for arbitrarily strong driving fields, 542-9 Molecular quadrupole moment of naphthalene, 1249-53 KINETICS Rate constants for the reactions of methylperoxy radicals with peroxy radicals, nitric oxide, and nitrogen dioxide using molecular modulation spectrometry, 153-63 Kinetic study of the reactions of hydrogen and deuterium atoms with hydrogen bromide and deuterium bromide by time-resolved resonance fluorescence, 276-85 Kinetic matrix effects (response and density distribution functions): ring closure.Reaction of indolinobe- nzospiropyrans in glassy poly(alky1 methacrylates), 35 1-68 Kinetic study of ground state atomic nitrogen, N(24S3.2),by time-resolved atomic resonance fluorescence 60619 Halide ion induced quenching and enhancement of the fluorescence of fluoranthene solubilized in cetyltrimethylammonium bromide micelles, 68 5-92 Reactions forming electronically-excited free radicals.Part 1. Ground-state reactions involving nitrogen mono- and difluoride, 71 1-28 On the NH proton tunneling rate in meso-tetraphenylporphine,729-3 1 Kinetics and photochemistry of the nitrate radical. Part 1. Absolute absorption cross section, 785-93 Reactions of carbon dioxide, carbon dioxide dimer, and water cations with various neutral molecules, 1084-92 Theory of the kinetic isotope effect in proton transfer reactions in a polar medium, 1128-46 Reactions of chlorofluoromethylene radicals studied by laser-induced fluorescence, 130H 3 Vibrational energy transfer from carbon monoxide (v = l), nitrogen (v = 1) carbon dioxide(001), J.C.S.FARADAY I1 SUBJECT INDEX VOL. 76 (1980) KINETICS(contd)nitrous oxide(001), and carbonyl sulfide(001) to ozone, 1354-70 Photochemistry of manganese porphyrins. Part 3. Interconversion of manganese(I1) and manganese(III), 141 5-28 Reactions forming electronically-excited free radicals. Part 2. Formation of nitrogen 4S, 2D, and 2P atoms in the hydrogen atom + difluoroamidogen reaction, and nitrogen atom reactions, 1543-60 KRYTOX Viscous, viscoelastic and dielectric properties of a perfluorinated polymer, Krytox 143-AB, 205-16 KWONG Prediction of phase equilibriums using the Redlich-Kwong equation of state, 1045-9 LASER Laser-induced fluorescence of iodine monobromide: the B3II(O +) excited state, 49-66 Quantum-resolved dynamics of excited states.Part 5. The long-lived A3lT(l,) state of bromine, 177-96 Kinetics of excited states of bromine using laser excitation. Part 2. Radiative lifetime and collisional deactivation of the B3II(O+,) state, 405-19 Pulsed source thermal lens. Part 1. Theoretical analysis, 63347 Laser-excitation studies of bromine. Collisional energy transfer involving resolved quantum states of excited Br2B311(OU +), 961-78 Laser-induced fluorescence studies: the B-X transition of chlorine. Part 5. Radiative lifetime of the B state, 1275-92 Reactions of chlorofluoromethylene radicals studied by laser-induced fluorescence, 1304-1 3 Laser-induced fluorescence studies: the B-X transition of chlorine. Part 6.Rotationally-dependent predissociation, 1561-8 Quantum-resolved dynamics of excited states. Part 6. Radiative lifetime and collisional deactivation rates in bromine fluoride fB). 1569-85 LATTICE , ,I Nuclear magnetic resonance spin-lattice relaxation and barriers in ethylenediammonium chloride, bromide, iodide, and sulfate, 1 196-207 Structure and dynamics of a new phase of anthracene, 133H6 Local configurations in cubic adamantane. Part 1, 1586-9 1 LAYER Thermodynamic approach to the interpretation of electrokinetic data near the isoelectric point, 1254-67 Theory of the electric double layer using a modified Poisson-Boltzmann equation, 1388-408 LEAD Oxidation of polycrystalline and (1 11) lead surfaces studied by electron spectroscopy, 267-75 LECITHIN Electron paramagnetic resonance and nuclear magnetic resonance studies of lipid-water systems, 96-100 LENGTH Microwave spectrum and barrier to internal rotation of 2-methyl-2-nitropropane, 330-8 LENNARD Solvent structure in particle interactions.Low pressure effects and analytic limits, 776-84 Fifth virial coefficient for the Lennard-Jones fluid in two dimensions. Integral equation results, 812-21 LENS Pulsed source thermal lens. Part 1. Theoretical analysis, 63347 LEVEL Quantum-resolved dynamics of excited states. Part 5. The long-lived A3n( 1,) state of bromine, 177-96 Kinetic spectroscopy in the far vacuum ultraviolet.Part 5. Oscillator strengths for the 3s, 4s, 5s, 3d and 4d 4P~-2p3 4,503.2 transitions in atomic nitrogen, 369-82 Lowest excited states of aza-analogs of stilbene. INDO/S calculation, 598-605 Emission spectra of the cations of cyanodiacetylene, methylcyanodiacetylene and ethylcyanodiacetylene in the gaseous phase. -A(rl) + -X(r1) band systems, 676-84 Dynamic solvation. Ionic vibrations in nonstationary solvation shells, 1026-44 LIB RATION Power reflection spectroscopy near the Brewster angle. Molecular dynamics of liquids, 1 147-60 Carbon-1 3 nuclear magnetic resonance study of molecular motions in natural rubber, 1219-23 LIFETIME Positron lifetime study of the transition from glassy to normal liquid state for two phenyl ethers, 225-32 Kinetics of excited states of bromine using laser excitation.Part 2. Radiative lifetime and collisional deactivation of the B3II(O+,) state, 405-19 Laser-induced fluorescence studies: the B-X transition of chlorine. Part 5. Radiative lifetime of the B state, 1275-92 Laser-induced fluorescence studies: the B-X transition of chlorine. Part 6. Rotationally-dependent predissociation, 1561-8 Quantum-resolved dynamics of excited states. Part 6. Radiative lifetime and collisional deactivation rates in bromine fluoride (B), 1569-85 LIGAND Contributions of orbital angular momentum to ligand hyperfine interactions in paramagnetic metal complexes, 660-6 26 J.C.S. FARADAY I1 SUBJECT INDEX VOL. 76 (1980) LIGHT Depolarized light scattering from gases of anisotropic molecules at intermediate pressures, 309-1 5 Light scattering study of the diffusion of interacting particles, 767-75 LIPID Electron paramagnetic resonance and nuclear magnetic resonance studies of lipid-water systems, 961 00 LITHIUM Atomization energies of the molecules LiSiO(g) and SizOz(g) by mass spectrometric gaseous equilibriums 447-52 LOCAL Local configurations in cubic adamantane.Part 1,1586-91 LOSS Diffusion equation for the nematic phase dielectric loss, 217-20 LUMINESCENCE Luminescence and 4A2+ 2E,2T, absorption spectrum of hexaureachromium(II1) iodide and hexaureaalu- minum(II1) iodide :hexaureachromium(III), 82-7 Vibrational structure in the luminescence spectra of uranium-doped tungstates with ordered perovskite structure, 872-84 The 4Azg <-> 2E, transitions in trans-dichlorobis(ethylenediamine)chromium(1+ ) and trans- dichlorobis(1,3-diarninopropane)chromium(1+), 138 1-7 Reactions forming electronically-excited free radicals.Part 2. Formation of nitrogen 4S, 2D, and 2P atoms in the hydrogen atom + difluoroamidogen reaction, and nitrogen atom reactions, 1543-60 MAGNETIC Electron paramagnetic resonance and nuclear magnetic resonance studies of lipid-water systems, 96-1 00 Study of molecular motion in tert-butyl halides by pulsed proton magnetic resonance, 550-5 Magnetic susceptibility of expanded liquid selenium, 75660 Nuclear magnetic resonance spin-lattice relaxation and barriers in ethylenediammonium chloride, bromide, iodide, and sulfate, 1 196207 Carbon-1 3 nuclear magnetic resonance study of molecular motions in natural rubber, 1219-23 Quadrupole moment and magnetic anisotropy of carbon disulfide, 1245-8 Magnetic birefringence in liquids of near-isotropic molecules, 161N 7 MAGNETISM Influence of the nonmagnetic cation upon the sign of the chromium(III)-chromium(III) coupling in trirutile compounds MCr206 (M = Te, W), 1224-33 MAGNETOOPTICAL Magnetooptical studies of liquid mixtures.Part 4. Additivity of the Faraday effect, the magnetic rotation dispersion constant, and the excess magnetic rotation in binary liquid mixtures, 1324-35 MAGNETOOPTICS Magnetooptical studies of liquid mixtures. Part 4. Additivity of the Faraday effect, the magnetic rotation dispersion constant, and the excess magnetic rotation in binary liquid mixtures, 1324-35 MANGANESE Electron paramagnetic resonance and nuclear magnetic resonance studies of lipid-water systems, 96- 100 Photoelectron spectra and electronic structure of the transition metal dichlorides, MC12 (M = chromium, manganese, iron, cobalt, nickel), 50619 Photochemistry of manganese porphyrins.Part 3. Interconversion of manganese(I1) and manganese(III), 1415-28 Photochemistry of manganese porphyrins. Part 4. Photosensitized reduction of quinones, 1429-41 MANNICH Dielectric relaxation studies in some phenolic Mannich bases, 589-97 MARANGONI Marangoni instability at a spherical interface. Breakdown of fluid drops at low surface tension and cytokinetic phenomena in the living cell, 1170-95 MARKOVIAN Non-Gaussian, non-Markov processes, 761-6 MATERIAL Viscous, viscoelastic and dielectric properties of a perfluorinated polymer, Krytox 143-AB, 205-16 MATRIX Kinetic matrix effects (response and density distribution functions): ring closure.Reaction of indolinobe- nzospiropyrans in glassy poly(alky1 methacrylates), 351-68 MCD Absorption, circular dichroism and magnetic circular dichroism spectra of trisodium praseodymium tris(0xydiacetate) di(sodium perchlorate) hexahydrate, 620-32 MECHANOCHEM Marangoni instability at a spherical interface. Breakdown of fluid drops at low surfacetension and cytokinetic phenomena in the living cell, 1170-95 MELT Hard-sphere model of fused salts, 1347-53 MEMBRANE Infrared investigation of water structurein desalinationmmbmes, 136-417 J.C.S.FARADAY I1 SUBJECT INDEX VOL. 76 (1980) METAL Optical properties of [M(L-L)~M(L-L)~XJ](C~O&,(M = platinum, palladium; L-L = 1,24iaminoeth-ane or 1,2-diaminopropane; X = chlonne, bromine, iodine): bulk and small particles, 104-1 1 Photoelectron spectra and electronic structure of the transition metal dichlorides, MC12 (M = chromium, manganese, iron, cobalt, nickel), 506-1 9 Contributions of orbital angular momentum to ligand hyperfine interactions in paramagnetic metal complexes, 660-6 Study of the semiconductor-to-metal transition in vanadium dioxide and vanadium sesquioxide by ultraviolet photoelectron spectroscopy, 929-35 Analysis of the vibrational spectrum of symmetrically solvated alkali metal cations, 979-1007 Indolyl alkali metal ion pairs in the excited state.Part 3. Solvent-excited solute relaxation in the S1-and TI-states, 1664-7 1 METHACRYLATE Kinetic matrix effects (response and density distribution functions): ring closure. Reaction of indolinobe- nzospiropyrans in glassy poly(alky1 methacrylates), 351-68 METHANE CH bond dipole, 172-6 Microwave spectra of bromotrifluoromethane and iodotrifluoromethane. Structures and dipole moments 339-50 Photoelectron spectra of nitrosomethane, tert-nitrosobutane and some perhalonitrosomethanes, 844-59 Reactions of carbon dioxide, carbon dioxide dimer, and water cations with various neutral molecules, 1084-92 Nitric oxide and difluoromethylene fluorescence during vacuum ultraviolet photodissociation of chlorodifluoronitrosomethane, 1409-14 METHYL Microwave spectrum and barrier to internal rotation of 2-methyl-2-nitropropane, 330-8 Source of anomalous fluorescence from solutions of 4'-N,N'+iimethylaminobenzonitrile in polar solvents, 453-7 1 Study of solvation models.Interpretation of solvent effect on the n* <-n transition of methyl acetate, 490-5 Microwave spectrum of acetyl isocyanate, 1208-1 3 Charge-cxchange mass spectra of ethyl acetate, methyl propionate, and propyl formate, 1450-7 Inelastic neutron scattering spectra of partially deuterated dimethylmethylphosphonates,1485-93 Attempted photoproduction of hydrogen using sulfophthalocyanines as chromophores for three- component systems, 1618-26 METHYLAMINE Infrared studies of complexes between carboxylic acids and tertiary amines in argon matrixes, 834-43 METHYLAMINO Source of anomalous fluorescence from solutions of 4'-N,N'4imethylaminobenzonitrile in polar solvents, 453-71 METHYLAMINOBENZONITRILE Source of anomalous fluorescence from solutions of 4'-N,N'-dimethylaminobenzonitrilein polar solvents, 453-71 METHYLAMMONIUM Ultrasonic relaxation of surfactants in water and deuterium oxide solutions, 794-802 METHYLANTHRACENE Mechanisms of singlet energy transfer in doped anthracene crystals at 5 K, studied by nanosecond spectrofluorimetry, 472-89 METHYLBENZENE Quadrupole moments of benzene, hexafluorobenzene and other nondipolar aromatic molecules, 648-59 METHYLCYANO Source of anomalous fluorescence from solutions of 4'-N,N'-dimethylaminobenzonitrile in polar solvents, 453-71 METHYLCYANOBENZONITRILE Source of anomalous fluorescence from solutions of 4'-N,N'-dimethylaminobenzonitrile in polar solvents, 453-71 METHYLCYANODIACETYLENE Emission spectra of the cations of cyanodiacetylene, methylcyanodiacetylene and ethylcyanodiacetylene in the gaseous phase.-A(.rrl) +-X(rl)band systems, 676-84 METHYLCYANOHYDRO Source of anomalous fluorescence from solutions of 4'-N,N'-dimethylaminobenzonitrile in polar solvents, 453-71 METHYLCYANOHYDROQUINOLINESource of anomalous fluorescence from solutions of 4'-N,N'-dimethylaminobenzonitrile in polar solvents, 453-71 METHYLCYANOINDOLINE Source of anomalous fluorescence from solutions of 4'-N,N+iimethylaminobenzonitrile in polar solvents. 453-71 J.C.S.FARADAY I1 SUBJECT INDEX VOL. 76 (1980) METHYLHYDROXY Electronic structure and assignment of the ultraviolet photoelectron spectra of 6-methyl-2-oxepyridine complexes of dichromium(I1) and dimolybdenum(II), 885-94 METHYLHYDROXYPY RIDINE Electronic structure and assignment of the ultraviolet photoelectron spectra of 6-methyl-2-0x0-pyridine complexes of dichromium(I1) and dimolybdenum(II), 885-94 METHYLMERCURY External pressure effect on quenching of benz[a]anthracene and 9-cyanoanthracene fluorescence by dimethylmercury, 324-9 METHYLNITROPHENYLBENZOSPIROPYRANINDOLINE Kinetic matrix effects (response and density distribution functions): ring closure. Reaction of indolinobe- nzospiropyrans in glassy poly(alky1 methacrylates), 35 1-68 METHYLNITROPROPANE Microwave spectrum and barrier to internal rotation of 2-methyl-2-nitropropane, 330-8 METHYLPEROXY Rate constants for the reactions of methylperoxy radicals with peroxy radicals, nitric oxide, and nitrogen dioxide using molecular modulation spectrometry, 1 53-63 METHYLPHOSPHONATE Inelastic neutron scattering spectra of partially deuterated dimethylmethylphosphonates,1485-93 METHY LTIN Magnetic birefringence in liquids of near-isotropic molecules, 1610-1 7 MICELLE Halide ion induced quenching and enhancement of the fluorescence of fluoranthene solubilized in cetyltrimethylammonium bromide micelles, 685-92 Ultrasonic relaxation of surfactants in water and deuterium oxide solutions, 794-802 Ultrasonic relaxation studies of sodium octyl sulfate complexes with synthetic polymers and a protein in aqueous solution, 1535-42 MICROEMULSION Light scattering study of the diffusion of interacting particles, 767-75 MICROWAVE Microwave spectrum and barrier to internal rotation of 2-methyl-2-nitropropane, 330-8 Microwave spectra of bromotrifluoromethane and iodotrifluoromethane.Structures and dipole moments 339-50 Microwave spectrum and conformation of triformylmethane, 383-90 Microwave spectrum of acetyl isocyanate, 1208-1 3 Molecular structure of 1,2-dimethyl-l,24iazetidine. Electron diffraction and microwave study and normal coordinate analysis, 1293-303 MIXING Thermodynamics of poly(dimethylsi1oxane) solutions, 895-904 MIXT Evaluation of the van der Waals constant, internal pressure, and sound velocity in binary liquid mixtures from Flory’s theory, 121 5-1 8 MNDO Multipole analysis of MNDO results, 302-8 MO Electronic structure and valence ionization energies of trichlorooxochromium studied by ab initio and SW-Xa methods, 164-7 1 Multipole analysis of MNDO results, 302-8 High resolution ultraviolet photoelectron spectra of monohalo- and p-dihalobenzenes, 556-70 Electronic structure and assignment of the ultraviolet photoelectron spectra of &methyl-2-0x0-pyridine complexes of dichromium(I1) and dimolybdenum(II), 885-94 SCF-Xa study of the electronic structure of tetrahalomethanes, tetrahalosilanes, and tetrafluorogermane 1375-80 Study by high-temperature photoelectron spectroscopy of the electronic structure of the transition metal difluorides, cupric fluoride and zinc fluoride, 1672-82 MOESSBAUER Influence of the nonmagnetic cation upon the sign of the chromium(III~hromium(III)coupling in trirutile compounds MCr206 (M = Te, W), 1224-33 MOL Static and dynamic Kerr-effect studies of glycerol in its highly viscous state, 112-21 Hybrid potential function for bound diatomic molecules, 129-35 CH bond dipole, 172-6 Calculations on the ground states of hydrogen cyanide monocation and hydrogen isocyanide monocatio- n, 319-23 Microwave spectrum and barrier to internal rotation of 2-methyl-2-nitropropane, 330-8 Microwave spectra of bromotrifluoromethane and iodotrifluoromethane. Structures and dipole moments 339-50 Microwave spectrum and conformation of triformylmethane, 383-90 Cusped-Gaussian molecular wave functions. Part 3.Basis sets for the first-row atoms, 391-404 J.C.S. FARADAY I1 SUBJECT INDEX VOL. 76 (1980) MOL(con td) Kinetics of excited states of bromine using laser excitation. Part 2. Radiative lifetime and collisional deactivation of the Bm(O+ u) state, 405-1 9 Study of molecular motion in tert-butyl halides by pulsed proton magnetic resonance, 550-5 High resolution ultraviolet photoelectron spectra of monohalo- and p-dihalobenzenes, 556-70 Carbon-1 3 and nitrogen-14 nuclear magnetic resonance study of triethylenediamine, 57 1-3 Dielectric relaxation studies in some phenolic Mannich bases, 589-97 Non-Gaussian, non-Markov processes, 761-6 Reactions of carbon dioxide, carbon dioxide dimer, and water cations with various neutral molecules, Power reflection spectroscopy near the Brewster angle.Molecular dynamics of liquids, 1 147-60 Molecular structure of 1,2-dimethyl-l,2-diazetidine.Electron diffraction and microwave study and normal coordinate analysis, 1293-303 Solvation forces in molecular fluids, 1478-84 Molecular dynamics simulation of a soft-disk system, 1646-54 MOLAR Determination of partial molar quantities in multicomponent systems, 1 1 19-27 MOLYBDENUM Electronic structure and assignment of the ultraviolet photoelectron spectra of 6-methyl-2-oxo-pyridinecomplexes of dichromium(I1) and dimolybdenum(II), 885-94 MOMENTUM Contributions of orbital angular momentum to ligand hyperfine interactions in paramagnetic metal complexes, 66&6 MONOLAYER Theory of cooperative phenomena in monolayers of hydroxyhexadecanoic acid isomers, 43 1-40 MONOMER Ultrasonic relaxation of surfactants in water and deuterium oxide solutions, 794-802 MONOSULFIDE Energy transfer from state-selected photofragments.Electronic quenching of CS(A~II),-&S,91 5-22 MORI Non-Gaussian, non-Markov processes, 761-6 MOUTON Molecular quadrupole moment of naphthalene, 1249-53 MULTICOMPONENT Determination of partial molar quantities in multicomponent systems, 1 119-27 MULTIPOLE Multipole analysis of MNDO results, 302-8 NAPHTHALENE Molecular quadrupole moment of naphthalene, 1249-53 NATURAL Carbon-1 3 nuclear magnetic resonance study of molecular motions in natural rubber, 1219-23 NEUTRON Inelastic neutron scattering spectra of partially deuterated dimethylmethylphosphonates,1485-93 NICKEL Photoelectron spectra and electronic structure of the transition metal dichlorides, MCl2 (M = chromium, manganese, iron, cobalt, nickel), 506-1 9 NITRATE Kinetics and photochemistry of the nitrate radical.Part 1. Absolute absorption cross section, 785-93 Heat capacity of bis(adiponitrile)copper(I)nitrate. An order-disorder transition in a dilute system of nitrate ions, 803-1 1 NITRIC Rate constants for the reactions of methylperoxy radicals with peroxy radicals, nitric oxide, and nitrogen dioxide using molecular modulation spectrometry, 1 53-63 Reactions of carbon dioxide, carbon dioxide dimer, and water cations with various neutral molecules, 1084-92 Reactions of chlorofluoromethylene radicals studied by laser-induced fluorescence, 1304-1 3 Nitric oxide and difluoromethylene fluorescence during vacuum ultraviolet photodissociation of chlorodifluoronitrosomethane, 1409-14 Reactions forming electronically-excited free radicals.Part 2. Formation of nitrogen 4S, 2D, and 2P atoms in the hydrogen atom + difluoroamidogen reaction, and nitrogen atom reactions, 1543-60 NITRILE Ionic and neutral optical emissions induced by helium(1ol) excitation of nitriles, 1079-83 NITRO Microwave spectrum and barrier to internal rotation of 2-methyl-2-nitropropane, 330-8 Electron spin resonance studies of ion association.Part 8. Effects of ion-pairing on nitrogen-14 hyperfine splittings in psubstituted nitrobenzene anions, 822-6 NITROBENZENE Electron spin resonance studies of ion association. Part 8. Effects of ion-pairing on nitrogen-14 hyperfine splittings in psubstituted nitrobenzene anions, 822-6 30 J.C.S. FARADAY I1 SUBJECT INDEX VOL. 76 (1980) NITROGEN Rate constants for the reactions of methylperoxy radicals with peroxy radicals, nitric oxide, and nitrogen dioxide using molecular modulation spectrometry, 153-63 Depolarized light scattering from gases of anisotropic molecules at intermediate pressures, 309-1 5 Microwave spectrum and barrier to internal rotation of 2-methyl-2-nitropropane, 330-8 Kinetic spectroscopy in the far vacuum ultraviolet. Part 5.Oscillator strengths for the 3s, 4s, 5s, 3d and 4d 4P~-2p3 4S03.2 transitions in atomic nitrogen, 369-82 Cusped-Gaussian molecular wave functions. Part 3. Basis sets for the first-row atoms, 391-404 Carbon-1 3 and nitrogen-14 nuclear magnetic resonance study of triethylenediamine, 57 1-3 Kinetic study of ground state atomic nitrogen, N(24S3.2), by time-resolved atomic resonance fluorescence 606-19 Reactions forming electronicdlly-excited free radicals. Part 1. Ground-state reactions involving nitrogen man+ and difluoride, 7 11-28 Energy transfer from state-selected photofragments. Electronic quenching of CS(AlII),%5,915-22Laser-excitation studies of bromine. Collisional energy transfer involving resolved quantum states of excited Br2B3II(OU+), 961-78 Reactions of carbon dioxide, carbon dioxide dimer, and water cations with various neutral molecules, 1084-92 Laser-induced fluorescence studies: the B-X transition of chlorine.Part 5. Radiative lifetime of the B state, 1275-92 Reactions of chlorofluoromethylene radicals studied by lase-induced fluorescence, 1304-1 3 Vibrational energy transfer from carbon monoxide (v = I), nitrogen (v = 1) carbon dioxide(001), nitrous oxide(001), and carbonyl sulfide(001) to ozone, 1354-70 Reactions forming electronically-excited free radicals. Part 2. Formation of nitrogen 4S, 2D, and 2P atoms in the hydrogen atom + difluoroamidogen reaction, and nitrogen atom reactions, 1543-60 NITROSO Photoelectron spectra of nitrosomethane, tert-nitrosobutane and some perhalonitrosomethanes, 844-59 NITROSOBUTANE Photoelectron spectra of nitrosomethane, tert-nitrosobutane and some perhalonitrosomethanes, 844-59 NITROSOMETHANE Photoelectron spectra of nitrosomethane, tert-nitrosobutane and some perhalonitrosomethanes, 844-59 Nitric oxide and difluoromethylene fluorescence during vacuum ultraviolet photodissociation of chlorodifluoronitrosomethane, 1409-14 NITROUS Kinetic study of ground state atomic nitrogen, N(24S3.2), by time-resolved atomic resonance fluorescence 606-19 Vibrational energy transfer from carbon monoxide (v = l), nitrogen (v = 1) carbon dioxide(001), nitrous oxide(001), and carbonyl sulfide(001) to ozone, 1354-70 NMR Electron paramagnetic resonance and nuclear magnetic resonance studies of lipid-water systems, 961 00 Study of molecular motion in tert-butyl halides by pulsed proton magnetic resonance, 55&5 Carbon-1 3 and nitrogen-14 nuclear magnetic resonance study of triethylenediamine, 571-3 On the NH proton tunneling rate in meso-tetraphenylporphine, 729-3 1 Influence of screening of intramolecular easily polarizable hydrogen bonds on their infrared absorbance, 1061-6 Carbon-1 3 nuclear magnetic resonance study of molecular motions in natural rubber, 1219-23 Viscosity dependent internal conversion in the rhodamine dye, Fast Acid Violet 2R, 1627-37 NQRZeeman effect of chlorine nuclear quadrupole resonance and hydrogen bonding in 2,&, 23, and 33- dichlorophenols, 1055-60 NUCLEATION Condensation modeling for highly supersaturated vapors: application to iron, 1494-5 15 NUCLEUS Cusped-Gaussian molecular wave functions.Part 3. Basis sets for the first-row atoms, 391-404 OCTANOATE Ultrasonic relaxation of surfactants in water and deuterium oxide solutions, 794-802 OCTYL Ultrasonic relaxation of surfactants in water and deuterium oxide solutions, 794-802 Ultrasonic relaxation studies of sodium octyl sulfate complexes with synthetic polymers and a protein in aqueous solution, 1535-42 OIL Light scattering study of the diffusion of interacting particles, 767-75 Marangoni instability at a spherical interface. Breakdown of fluid drops at low surface tension and cytokinetic phenomena in the living cell, 1170-95 OPPENHEIMER Dynamic solvation.Ionic vibrations in nonstationary solvation shells, 1026-44 ORBITAL Contributions of orbital angular momentum to ligand hyperfine interactions in paramagnetic metal complexes, 66&6 J.C.S. FARADAY I1 SUBJECT INDEX VOL. 76 (1980) ORDER Absorption, circular dichroism and magnetic circular dichroism spectra of trisodium praseodymium tris(0xydiacetate) di(sodium perchlorate) hexahydrate, 620-32 Heat capacity of bis(adiponitrile)copper(I)nitrate. An order4isorder transition in a dilute system of nitrate ions, 803-1 1 Molecular dynamics simulation of a soft-disk system, 164654 ORGANOTIN Structure and fluxional behavior of the adducts of orthoquinones with organotin halides.An electron spin resonance study, 948-53 0RI ENTATI ON Local configurations in cubic adamantane. Part 1. 158691" ORTHO Structure and fluxional behavior of the adducts of orthoauinones with organotin halides. An electron Y spin resonance study, 948-53 ORTHOQUINONE Structure and fluxional behavior of the adducts of orthoquinones with organotin halides. An electron spin resonance study, 948-53 ORTHORHOMBIC Cluster groups, 534-41 OSCILLATION Dynamic solvation. Ionic vibrations in nonstationary solvation shells, 1026-44 OSCILLATOR Kinetic spectroscopy in the far vacuum ultraviolet. Part 5. Oscillator strengths for the 3s, 4s, 5s, 3d and 4d 4P~-2p3 4SO3.2 transitions in atomic nitrogen, 369-82 Lowest excited states of ma-analogs of stilbene.INDO/S calculation, 598-605 Some model potentials for the ammoniated electron, 1592-8 OSMATE Resonance Raman, infrared, and electronic spectral studies of p-oxo-decahalodimetallate speciesosmium, rhenium, ruthenium, and tungsten, 1 103-1 8 OVERHAUSER Carbon-1 3 nuclear magnetic resonance study of molecular motions in natural rubber, 1219-23 OXIDE Rate constants for the reactions of methylperoxy radicals with peroxy radicals, nitric oxide, and nitrogen dioxide using molecular modulation spectrometry, 153-63 Atomization energies of the molecules LiSiO(g) and Si202(g) by mass spectrometric gaseous equilibriums 447-52 Kinetic study of ground state atomic nitrogen, N(24S3.2), by time-resolved atomic resonance fluorescence 606- 19 Energy transfer from state-selected photofragments.Electronic quenching of CS(AlII),-(t$, 91 5-22 Study of the semiconductor-to-metal transition in vanadium dioxide and vanadium sesquioxide by ultraviolet photoelectron spectroscopy, 929-35 Influence of screening of intramolecular easily polarizable hydrogen bonds on their infrared absorbance, 10614 Reactions of carbon dioxide, carbon dioxide dimer, and water cations with various neutral molecules, 108492 Influence of the nonmagnetic cation upon the sign of the chromium(III~hromium(III)coupling in trirutile compounds MCr206 (M = Te, W), 1224-33 Reactions of chlorofluoromethylene radicals studied by laser-induced fluorescence, 1304-1 3 Vibrational energy transfer from carbon monoxide (v = l), nitrogen (v = 1) carbon dioxide(001), nitrous oxide(001), and carbonyl sulfide(001) to ozone, 1354-70 Nitric oxide and difluoromethylene fluorescence during vacuum ultraviolet photodissociation of chlorodifluoronitrosomethane,1409-1 4 Reactions forming electronically-excited free radicals.Part 2. Formation of nitrogen 4S, 2D, and 2P atoms in the hydrogen atom + difluoroamidogen reaction, and nitrogen atom reactions, 1543-60 OXIDN Oxidation of polycrystalline and (111) lead surfaces studied by electron spectroscopy, 267-75 Photochemistry of manganese porphyrins. Part 3. Interconversion of manganese(I1) and manganese(III), 1415-28 OX0 Resonance Raman, infrared, and electronic spectral studies of p-oxo-decahalodimetallate speciesosmium, rhenium, ruthenium, and tungsten, 1103-18 OXOCHLORO Electronic structure and valence ionization energies of trichlorooxochromium studied by ab initio and SW-Xu methods, 164-71 OXOCHROMIUM Electronic structure and valence ionization energies of trichlorooxochromium studied by ab initio and SW-Xa methods, 16471 OXODECACHLORO Resonance Raman, infrared, and electronic spectral studies of p-oxo-decahalodimetallate species J.C.S.FARADAY I1 SUBJECT INDEX VOL. 76 (1980) OXODECACHLORO(contd)osmium, rhenium, ruthenium, and tungsten, 1103-18 OXODECAH ALO Resonance Raman, infrared, and electronic spectral studies of p-oxo-decahalodimetallate speciesosmium, rhenium, ruthenium, and tungsten, 1103-18 OXODECAHALODIMETALLATE Resonance Raman, infrared, and electronic spectral studies of p-oxociecahalodimetallate speciesosmium, rhenium, ruthenium, and tungsten, 1103-18 OXYANION SCF-Xa investigation of the ionization energies of perchlorate, sulfate, and phosphate anions, 441-5 OXYDIACETATE Absorption, circular dichroism and magnetic circular dichroism spectra of trisodium praseodymium tris(oxydiacetate) di(sodium perchlorate) hexahydrate, 620-32 OXYGEN Oxidation of polycrystalline and (1 1 1) lead surfaces studied by electron spectroscopy, 267-75 Cusped-Gaussian molecular wave functions.Part 3. Basis sets for the first-row atoms, 391-404 Reactions forming electronically-excited free radicals. Part 1. Ground-state reactions involving nitrogen mono- and difluoride, 7 1 1-28 Vibrational relaxation of excited oxygen 02(lA&, studied with a discharge-flow-shock-tube technique,923-8 Reactions of carbon dioxide, carbon dioxide dimer, and water cations with various neutral molecules, 1084-92 Laser-induced fluorescence studies: the B-X transition of chlorine. Part 5.Radiative lifetime of the B state, 1275-92 Reactions of chlorofluoromethylene radicals studied by laser-induced fluorescence, 1304-1 3 Photochemistry of manganese porphyrins. Part 3. Interconversion of manganese(I1) and manganese(III), 1415-28 A study of three dimol emissions of singlet oxygen, 02(lA ,using a discharge flow shock tube, 1442-9 Quantum-resolved dynamics of excited states. Part 6.Ra diative lifetime and collisional deactivation rates in bromine fluoride (B), 1569-85 OZONE Kinetic study of ground state atomic nitrogen, N(24S3.2), by time-resolved atomic resonance fluorescence 60619 Vibrational energy transfer from carbon monoxide (v = l), nitrogen (v = 1) carbon dioxide(001), nitrous oxide(001), and carbonyl sulfide(00 1) to ozone, 1354-70 PAIR Molecular dynamics simulation of a softaisk system, 1646-54 Indolyl alkali metal ion pairs in the excited state. Part 3. Solvent-excited solute relaxation in the S1- and TI-states, 1664-71 PAIRING Ion-pairing in aqueous media. An exact solution for the interaction energy associated with two dielectric spheres, 575-88 PALLADIUM Optical properties of [M(L-L)2M(L-L)2X2](Cl04)4, (M = platinum, palladium; L-L = 1,24iaminoeth-ane or 1,24iaminopropane; X = chlorine, bromine, iodine): bulk and small particles, 104-1 1 PARAMAGNETIC Magnetic susceptibility of expanded liquid selenium, 75660 PARAMAGNETISM Contributions of orbital angular momentum to ligand hyperfine interactions in paramagnetic metal complexes, 660-6 PARTICLE Optical properties of [M(L-L)2M(L-L)2X2](ClO&, (M = platinum, palladium; L-L = 1,24iaminoeth-ane or 1,2-diaminopropane; X = chlorine, bromine, iodine): bulk and small particles, 104-1 1 Light scattering study of the diffusion of interacting particles, 767-75 Solvent structure in particle interactions. Low pressure effects and analytic limits, 77684 PARTITIONING Intramolecular hydrogen bond in ortho-hydroxyazobenzenes,827-33 PERCHLORATE SCF-Xa investigation of the ionization energies of perchlorate, sulfate, and phosphate anions, 441-5 Absorption, circular dichroism and magnetic circular dichroism spectra of trisodium praseodymium tris(oxydiacetate) di(sodium perchlorate) hexahydrate, 620-32 Influence of screening of intramolecular easily polarizable hydrogen bonds on their infrared absorbance, 1061-6 PERCUS Solvent structure in particle interactions.Low pressure effects and analytic limits, 77684 Fifth virial coefficient for the Lennard-Jones fluid in two dimensions. Integral equation results, 8 12-21 PERFLUORO Viscous, viscoelastic and dielectric properties of a perfluorinated polymer, Krytox 143-AB, 205-16 Ultrasonic relaxation of surfactants in water and deuterium oxide solutions, 794-802 J.C.S.FARADAY I1 SUBJECT INDEX VOL. 76 (1980) PERMITTIVITY Dielectric relaxation studies in some phenolic Mannich bases, 589-97 PHASE Prediction of phase equilibriums using the Redlich-Kwong equation of state, 1045-9 Statistical thermodynamics of fluid phase equilibrium in a conformal polydisperse system, 1458-67 Phase separation in a polydisperse system, 1468-77 Molecular dynamics simulation of a soft-disk system, 1646-54 PHENOL Zeeman effect of chlorine nuclear quadrupole resonance and hydrogen bonding in 2,6-, 2,5-, and 3,s dichlorophenols, 1055-60 PHENYL Positron lifetime study of the transition from glassy to normal liquid state for two phenyl ethers, 225-32 PHENYLPORPHINE On the NH proton tunneling rate in meso-tetraphenylporphine, 729-3 1 PHOSPHATE SCF-Xa investigation of the ionization energies of perchlorate, sulfate, and phosphate anions, 441-5 PHOSPHONATE Inelastic neutron scattering spectra of partially deuterated dimethylmethylphosphonates,1485-93 PHOSPHORESCENCE Indolyl alkali metal ion pairs in the excited state. Part 3.Solvent-excited solute relaxation in the S1- and TI-states, 1664-7 1 PHOTO Nitric oxide and difluoromethylene fluorescence during vacuum ultraviolet photodissociation of chlorodifluoronitrosomethane, 1409-14 Some model potentials for the ammoniated electron, 1592-8 PHOTOCHEM Kinetics and photochemistry of the nitrate radical. Part 1. Absolute absorption cross section, 785-93 Photochemistry of manganese porphyrins.Part 3. Interconversion of manganese(I1) and manganese(III), 1415-28 PHOTOCHROMIC Kinetic matrix effects (response and density distribution functions): ring closure. Reaction of indolinobe-nzospiropyrans in glassy poly(alky1 methacrylates), 3 5 1-68 PHOTODIMERIZATION Photodimerization of benzyl9-anthroate in the presence of triethylamine. Role of exciplex and triplet formation, 1-1 3 PHOTODISSOCN Energy disposal in the vacuum ultraviolet photodissociation of carbon disulfide and carbon diselenide, 905-14 PHOTOELECTRON Photoelectron spectra of selenium dichloride and diselenium dichloride, 148-52 Electronic structure and valence ionization energies of trichlorooxochromium studied by ab initio and SW-Xa methods, 164-71 Oxidation of polycrystalline and (1 11) lead surfaces studied by electron spectroscopy, 267-75 Emission spectra of the cations of cyanodiacetylene, methylcyanodiacetylene and ethylcyanodiacetylene in the gaseous phase.-A(n-l) -+-X(&) band systems, 676-84 Photoelectron spectra of nitrosomethane, tert-nitrosobutane and some perhalonitrosomethanes, 844-59 Ionic and neutral optical emissions induced by helium(1a) excitation of nitriles, 1079-83 Charge-xchange mass spectra of ethyl acetate, methyl propionate, and propyl formate, 1450-7 PHOTOFRAGMENT Nitric oxide and difluoromethylene fluorescence during vacuum ultraviolet photodissociation of chlorodifluoronitrosomethane, 1409-1 4 PHOTOIONIZATION Some model potentials for the ammoniated electron, 1592-8 PHOTOLYSIS Kinetic study of ground state atomic nitrogen, N(24S3.2), by time-resolved atomic resonance fluorescence 606-1 9 Ionic and neutral optical emissions induced by helium(1a) excitation of nitriles, 1079-83 Nitric oxide and difluoromethylene fluorescence during vacuum ultraviolet photodissociation of chlorodifluoronitrosomethane, 1409-14 PHOTOPRODN Attempted photoproduction of hydrogen using sulfophthalocyanines as chromophores for three- component systems, 1618-26 PHOTOSENSITIZER Photochemistry of manganese porphyrins.Part 4. Photosensitized reduction of quinones, 1429-41 PHTHALOCYANINE Attempted photoproduction of hydrogen using sulfophthalocyanines as chromophores for three- component systems, 16 18-26 PI Polynomial matrix method for the estimation of ndectron energies of some linear conjugated molecules 34 J.C.S.FARADAY I1 SUBJECT INDEX VOL. 76 (1980) PI(contd)1161-9 PLANCK Non-Gaussian, non-Markov processes, 76 1-6 PLASMA Distribution of ions in electrolyte solutions and plasmas. Part 1, 1093-102 Distribution of ions in electrolyte solutions and plasmas. Part 2, 1599-609 PLATINUM Optical properties of [M(L-L)2M(L-L)2X2](ClO&, (M = platinum, palladium; L-L = 1,24iaminoeth-ane or 1,24iaminopropane; X = chlorine, bromine, iodine): bulk and small particles, 104-1 1 POINT Thermodynamic approach to the interpretation of electrokinetic data near the isoelectric point, 1254-67 POLAR Power reflection spectroscopy near the Brewster angle.Molecular dynamics of liquids, 1 147-60 POLARIZABILITY Polarizable acid-water hydrogen bonds with aqueous solutions of carboxylic acids, 14-25 POLARIZATION Nonlocal screening in a polar solvent, 67-81 POLARON Some model potentials for the ammoniated electron, 1592-8 POLYALKYL Kinetic matrix effects (response and density distribution functions): ring closure. Reaction of indolinobe- nzospiropyrans in glassy poly(alky1 methacrylates), 351-68 POLYDIMETHYL Thermodynamics of poly(dimethylsi1oxane) solutions, 895-904 POLYDIMETHYLSILOXANE Thermodynamics of poly(dimethylsi1oxane) solutions, 895-904 POLYDISPERSE Statistical thermodynamics of fluid phase equilibrium in a conformal polydisperse system, 1458-67 Phase separation in a polydisperse system, 1468-77 POLYIMIDE Infrared investigation of water structure in desalination membranes, 13W7 POLYMER Viscous, viscoelastic and dielectric properties of a perfluorinated polymer, Krytox 143-AB, 205-1 6 Thermodynamics of poly(dimethylsi1oxane) solutions, 895-904 Polynomial matrix method for the estimation of n-electron energies of some linear conjugated molecules 1161-9 Ultrasonic relaxation studies of sodium octyl sulfate complexes with synthetic polymers and a protein in aqueous solution, 1535-42 POLYMETHINE Polynomial matrix method for the estimation of n-electron energies of some linear conjugated molecules 1161-9 POLY METHYL Kinetic matrix effects (response and density distribution functions): ring closure.Reaction of indolinobe- nzospiropyrans in glassy poly(alky1 methacrylates), 35 1-68 POLYMORPH Structure and dynamics of a new phase of anthracene, 1336-46 POLYOXYETHYLENE Infrared investigation of water structure in desalination membranes, 13647 POLYOXYPROPYLENE Infrared investigation of water structure in desalination membranes, 136-47 POLYVINYL Ultrasonic relaxation studies of sodium octyl sulfate complexes with synthetic polymers and a protein in aqueous solution, 1535-42 POLYVINYLPY RIDINE Ultrasonic relaxation studies of sodium octyl sulfate complexes with synthetic polymers and a protein in aqueous solution, 1535-42 POLYVINYLPY RROLIDONE Ultrasonic relaxation studies of sodium octyl sulfate complexes with synthetic polymers and a protein in aqueous solution, 153542 PORPHINE On the NH proton tunneling rate in meso-tetraphenylporphine, 729-3 1 PORPHYRIN Photochemistry of manganese porphyrins. Part 3.Interconversion of manganese(I1) and manganese(III), 1415-28 Photochemistry of manganese porphyrins. Part 4. Photosensitized reduction of quinones, 1429-41 POSITRON Positron lifetime study of the transition from glassy to normal liquid state for two phenyl ethers, 225-32 J.C.S. FARADAY I1 SUBJECT INDEX VOL. 76 (1980) POSITRONIUM Positron lifetime study of the transition from glassy to normal liquid state for two phenyl ethers, 225-32 POTASSIUM Electronic transitions at the surface of potassium iodide microcrystals. Part 1.Surface states, 420-30 Helium I and helium I1 photoelectron spectra of alkali fluorides in the vapor phase, 1523-32 POTENTIAL Hybrid potential function for bound diatomic molecules, 129-35 Atomization energies of the molecules LiSiO(g) and Si202(g) by mass spectrometric gaseous equilibriums 447-52 Analysis of the vibrational spectrum of symmetrically solvated alkali metal cations, 979-1007 Distribution of ions in electrolyte solutions and plasmas. Part 1, 1093-102 Thermodynamic approach to the interpretation of electrokinetic data near the isoelectric point, 1254-67 Theory of the electric double layer using a modified Poisson-Boltzmann equation, 1388-408 Some model potentials for the ammoniated electron, 1592-8 PRASEODYMIUM Absorption, circular dichroism and magnetic circular dichroism spectra of trisodium praseodymium tris(0xydiacetate) di(sodium perchlorate) hexahydrate, 620-32 PREDISSOCN Laser-induced fluorescence of iodine monobromide: the Bm(O +) excited state, 49-66 Laser-induced fluorescence studies: the B-X transition of chlorine.Part 6. Rotationally-dependent predissociation, 1561-8 PRESSURE External pressure effect on quenching of benz[a]anthracene and 9-cyanoanthracene fluorescence by dimethylmercury, 324-9 Evaluation of the van der Waals constant, internal pressure, and sound velocity in binary liquid mixtures from Flory’s theory, 121 5-1 8 PRODN Attempted photoproduction of hydrogen using sulfophthalocyanines as chromophores for three- component systems, 161 8-26 PROFILE Solvation forces in molecular fluids, 1478-84 PROPANE Microwave spectrum and barrier to internal rotation of 2-methyl-2-nitropropane, 330-8 PROP ANENITRILE Ionic and neutral optical emissions induced by helium(1a) excitation of nitriles, 1079-83 PROPANOL Infrared studies and thermodynamics of hydrogen bonding in 2-chloroethanol,3-chloropropanol and 4-chlorobutanol, 233-49 PROPIONATE Charge-exchange mass spectra of ethyl acetate, methyl propionate, and propyl formate, 1450-7 PROPYL Charge*xchange mass spectra of ethyl acetate, methyl propionate, and propyl formate, 1450-7 PROTON On the NH proton tunneling rate in meso-tetraphenylporphine,729-3 1 Role of intermolecular forces in proton-transfer reactions, 954-60 Theory of the kinetic isotope effect in proton transfer reactions in a polar medium, 1128-46 PSEUDOHALIDE Low-frequency bending motions of the silyl pseudohalides SiH3NCY (Y = 0,S, Se).An experimental and theoretical study, 860-71 PY RIDINE Lowest excited states of aza-analogs of stilbene. INDO/S calculation, 598-605 Electronic structure and assignment of the ultraviolet photoelectron spectra of 6-methyl-2-0x0-pyridine complexes of dichromium(I1) and dimolybdenum(II), 885-94 PYRIDYL Lowest excited states of aza-analogs of stilbene. INDO/S calculation, 598-605 PYRIDYLETHYLENE Lowest excited states of aza-analogs of stilbene. INDO/S calculation, 598-605 PYROLLE Charge-exchange mass spectra of thiophene, pyrrole, and furan, 15 16-22 QUADRUPOLE Quadrupole moments of benzene, hexafluorobenzene and other nondipolar aromatic molecules, 648-59 Quadrupole moment and magnetic anisotropy of carbon disulfide, 12458 Molecular quadrupole moment of naphthalene, 1249-53 QUANTITY Determination of partial molar quantities in multicomponent systems, 11 19-27 QUENCHING Quantum-resolved dynamics of excited states.Part 5. The long-lived A3n(lU) state of bromine, 177-96 External pressure effect on quenching of benz[a]anthracene and Qyanoanthracene fluorescence by dimethylmercury, 324-9 36 J.C.S. FARADAY I1 SUBJECT INDEX VOL. 76 (1980) QUENCHING(contd)Kinetic study of ground state atomic nitrogen, N(24S3.2),by time-resolved atomic resonance fluorescence 606-19 Halide ion induced quenching and enhancement of the fluorescence of fluoranthene solubilized in cetyltrimethylammonium bromide micelles, 68592 Energy transfer from stateselected photofragments. Electronic quenching of CS(A1IIL-o-5,9 15-22 Laser-induced fluorescence studies: the B-X transition of chlorine.Part 5. Radiative lifetime of the B state, 127592 Nitric oxide and difluoromethylene fluorescence during vacuum ultraviolet photodissociation of chlorodifluoronitrosomethane, 1409-14 Quantum-resolved dynamics of excited states. Part 6. Radiative lifetime and collisional deactivation rates in bromine fluoride (B), 1569-85 QUINOLINE Source of anomalous fluorescence from solutions of 4'-N,N'-dimethylaminobenzonitrile in polar solvents, 453-71 QUINONEStructure and fluxional behavior of the adducts of orthoquinones with organotin halides.An electron spin resonance study, 948-53 Photochemistry of manganese porphyrins. Part 4. Photosensitized reduction of quinones, 1429-41 RADIATIVE Laser-induced fluorescence studies: the B-X transition of chlorine. Part 5. Radiative lifetime of the B state, 1275-92 RADICAL Rate constants for the reactions of methylperoxy radicals with peroxy radicals, nitric oxide, and nitrogen dioxide using molecular modulation spectrometry, 153-63 Reactions forming electronically-excited free radicals. Part 1. Ground-state reactions involving nitrogen monw and difluoride, 71 1-28 Kinetics and photochemistry of the nitrate radical. Part 1. Absolute absorption cross section, 785-93 Ionic and neutral optical emissions induced by helium(1a) excitation of nitriles, 1079-83 Reactions of chlorofluoromethvlene radicals studied bv laser-induced fluorescence.1304-13 RAMAN Vibrational sDectra of matrix isolated aluminum chloride dimer. IsotoDic fine structure and valence force field,&2&41 Resonance Raman, infrared, and electronic spectral studies of p-oxo-decahalodimetallate speciesosmium, rhenium, ruthenium, and tungsten, 110318 Molecular structure of 1,2-dimethyl-1,2-diazetidine. Electron diffraction and microwave study and normal coordinate analysis, 1293-303 RATE Transport properties in dilute gases: an approach using time-correlation functions. Part 1. Viscosity and thermal conductivity of gases and gas mixtures in which the exchange of molecular internal energy is slow, 735-46 Transport properties in dilute gases: an approach using time-correlation functions.Part 2. Viscosity and thermal conductivity of gases and gas mixtures in which the exchange of molecular internal energy is significant, 747-55 RATIO Depolarized light scattering from gases of anisotropic molecules at intermediate pressures, 309-1 5 REACTION Rate constants for the reactions of methylperoxy radicals with peroxy radicals, nitric oxide, and nitrogen dioxide using molecular modulation spectrometry, 1 53-63 Kinetic study of the reactions of hydrogen and deuterium atoms with hydrogen bromide and deuterium bromide by time-resolved resonance fluorescence, 276-85 Reactions forming electronically-excited free radicals.Part 1. Ground-state reactions involving nitrogen mono- and difluoride, 71 1-28 Reactions of carbon dioxide, carbon dioxide dimer, and water cations with various neutral molecules, 1084-92 Reactions of chlorofluoromethylene radicals studied by laser-induced fluorescence, 1304-13 Reactions forming electronically-excited free radicals. Part 2. Formation of nitrogen 4S, 2D, and 2P atoms in the hydrogen atom + difluoroamidogen reaction, and nitrogen atom reactions, 1543-60 RECOVERY Marangoni instability at a spherical interface. Breakdown of fluid drops at low surface tension and cytokinetic phenomena in the living cell, 1170-95 REDLICH Prediction of phase equilibriums using the Redlich-Kwong equation of state, 1045-9 REDN Photochemistry of manganese porphyrins. Part 3.Interconversion of manganese(I1) and manganese(III), 141 5-28 Photochemistry of manganese porphyrins. Part 4. Photosensitized reduction of quinones, 1429-41 REFLECTION Electronic transitions at the surface of potassium iodide microcrystals. Part 1. Surface states, 420-30 J.C.S. FARADAY I1 SUBJECT INDEX VOL. 76 (1980) REFLECTION(contd)Power reflection spectroscopy near the Brewster angle. Molecular dynamics of liquids, 1 147-60 RELAXATION Electron paramagnetic resonance and nuclear magnetic resonance studies of lipid-water systems, 96-1 00 Static and dynamic Kerr-effect studies of glycerol in its highly viscous state, 112-21 Viscous, viscoelastic and dielectric properties of a perfluorinated polymer, Krytox 143-AB, 205-16 Study of molecular motion in tert-butyl halides by pulsed proton magnetic resonance, 55&5 Carbon-1 3 and nitrogen-14 nuclear magnetic resonance study of triethylenediamine, 57 1-3 Dielectric relaxation studies in some phenolic Mannich bases, 589-97 Volume relaxation in simple liquids, 704-10 Ultrasonic relaxation of surfactants in water and deuterium oxide solutions, 794-802 Energy transfer from state-selected photofragments.Electronic quenching of CS(Alll),w~, 91 5-22 Vibrational relaxation of excited oxygen 02(lAg), studied with a discharge-flow-shock-tube technique, Laser-excitation studies of bromine. Collisional energy transfer involving resolved quantum states of excited Br2B3n(Ou+), 961-78 Nuclear magnetic resonance spin-lattice relaxation and barriers in ethylenediammonium chloride, bromide, iodide, and sulfate, 1 196-207 Carbon-1 3 nuclear magnetic resonance study of molecular motions in natural rubber, 1219-23 Ultrasonic relaxation studies of sodium octyl sulfate complexes with synthetic polymers and a protein in aqueous solution, 1535-42 Indolyl alkali metal ion pairs in the excited state.Part 3. Solvent-excited solute relaxation in the S1-and TI-states, 1664-71 REORIENTATION Study of molecular motion in tert-butyl halides by pulsed proton magnetic resonance, 550-5 Carbon-1 3 and nitrogen-14 nuclear magnetic resonance study of triethylenediarnine, 571-3 Nuclear magnetic resonance spin-lattice relaxation and barriers in ethylenediammonium chloride, bromide, iodide, and sulfate, 1 196207 REPULSION Analysis of the vibrational spectrum of symmetrically solvated alkali metal cations, 979-1007 RESONANCE Reactions forming electronically-excited free radicals.Part 1. Ground-state reactions involving nitrogen mono- and difluoride, 71 1-28 Resonance Raman, infrared, and electronic spectral studies of p-oxo-decahalodimetallate speciesosmium, rhenium, ruthenium, and tungsten, 1 103-1 8 REVIEW Marangoni instability at a spherical interface. Breakdown of fluid drops at low surface tension and cytokinetic phenomena in the living cell, 1170-95 RHENATE Resonance Raman, infrared, and electronic spectral studies of p-oxo-decahalodimetallate speciesosmium, rhenium, ruthenium, and tungsten, 1103-18 RHODAMINE Viscosity dependent internal conversion in the rhodamine dye, Fast Acid Violet 2R, 1627-37 Internal conversion in the rhodamine dye, Fast Acid Violet 2R, 1638-45 RING Thinning and rupture of ring-shaped films, 250-66 ROCKET Condensation modeling for highly supersaturated vapors: application to iron, 1494-5 15 ROTATION Far infrared solution spectra.Volume of rotation and effective torque, 286-301 Microwave spectrum and barrier to internal rotation of 2-methyl-2-nitropropane, 330-8 Dielectric relaxation studies in some phenolic Mannich bases, 589-97 Energy transfer from state-selected photofragments. Electronic quenching of CS(Alll),%s, 91 5-22 Laser-excitation studies of bromine. Collisional energy transfer involving resolved quantum states of excited Br2BTI(Ou+), 961-78 Microwave spectrum of acetyl isocyanate, 1208-1 3 Magnetooptical studies of liquid mixtures.Part 4. Additivity of the Faraday effect, the magnetic rotation dispersion constant, and the excess magnetic rotation in binary liquid mixtures, 1324-35 Inelastic neutron scattering spectra of partially deuterated dimethylmethylphosphonates,1485-93 Laser-induced fluorescence studies: the €3-X transition of chlorine. Part 6. Rotationally-dependent predissociation, 1561-8 ROTATIONAL Energy disposal in the vacuum ultraviolet photodissociation of carbon disulfide and carbon diselenide, 905-14 ROVIB RAT1 ON AL Laser-induced fluorescence studies: the EX transition of chlorine.Part 6. Rotationally-dependent predissociation, 1561-8 Quantum-resolved dynamics of excited states. Part 6. Radiative lifetime and collisional deactivation rates in bromine fluoride (B), 1569-85 J.C.S. FARADAY I1 SUBJECT INDEX VOL. 76 (1980) RUBBER Carbon-13 nuclear magnetic resonance study of molecular motions in natural rubber, 1219-23 RUBIDIUM Helium I and helium I1 photoelectron spectra of alkali fluorides in the vapor phase, 1523-32 RUPTURE Thinning and rupture of ring-shaped films, 25066 SALT Nuclear magnetic resonance spin-lattice relaxation and barriers in ethylenediammonium chloride, bromide, iodide, and sulfate, 1196-207 Hard-sphere model of fused salts, 1347-53 SCATTERING Depolarized light scattering from gases of anisotropic molecules at intermediate pressures, 309-1 5 Light scattering study of the diffusion of interacting particles, 767-75 Inelastic neutron scattering spectra of partially deuterated dimethylmethylphosphonates,1485-93 SCF Calculations on the ground states of hydrogen cyanide monocation and hydrogen isocyanide monocatio- n, 319-23 High resolution ultraviolet photoelectron spectra of monohalo- and p-dihalobenzenes, 556-70 SCRAMBLING Nonrigid molecules.Part 4.Hydrogen atom scrambling in the mass spectra of hydrocarbons, 88-95 SCREENING Nonlocal screening in a polar solvent, 67-81 Influence of screening of intramolecular easily polarizable hydrogen bonds on their infrared absorbance, 1061-6 SECTION Kinetics and photochemistry of the nitrate radical.Part 1. Absolute absorption cross section, 785-93 SELENIDE Energy disposal in the vacuum ultraviolet photodissociation of carbon disulfide and carbon diselenide, 905-14 SELENIUM Photoelectron spectra of selenium dichloride and diselenium dichloride, 148-52 Magnetic susceptibility of expanded liquid selenium, 756-60 SELF Study of self-association of tert-butyl alcohol by linear and nonlinear dielectric effects, 42-8 SEMICONDUCTOR Study of the semiconductor-to-metal transition in vanadium dioxide and vanadium sesquioxide by ultraviolet photoelectron spectroscopy, 929-35 SEPN Phase separation in a polydisperse system, 1468-77 SERUM Ultrasonic relaxation studies of sodium octyl sulfate complexes with synthetic polymers and a protein in aqueous solution, 153542 SET Cusped-Gaussian molecular wave functions.Part 3. Basis sets for the first-row atoms, 391404 SHAPE Thinning and rupture of ring-shaped films, 250-66 SHELL Dynamic solvation. Ionic vibrations in nonstationary solvation shells, 1026-44 SHOCK Vibrational relaxation of excited oxygen 02(1A&, studied with a discharge-flow-shock-tube technique,923-8 SILICON Atomization energies of the molecules LiSiO(g) and Si202(g) by mass spectrometric gaseous equilibriums 447-52 SILOXANE Thermodynamics of poly(dimethylsi1oxane) solutions, 895-904 SILYL Vibrational spectra and normal coordinate analysis of silyl pseudohalides. Part 1. Silyl isothiocyanate, 496-505 Low-frequency bending motions of the silyl pseudohalides SiH3NCY (Y = 0,S, Se).An experimental and theoretical study, 860-71 SIMULATION Non-Gaussian, non-Markov processes, 761-6 Brownian dynamics ofmany-body systems, 1067-78 Molecular dynamics simulation of a soft4isk system, 164654 SINGLET Mechanisms of singlet energy transfer in doped anthracene crystals at 5 K, studied by nanosecond spectrofluorimetry,472-89 A study of three dimol emissions of singlet oxygen, 02(lAg), using a discharge flow shock tube, 1442-9 J.C.S. FARADAY I1 SUBJECT INDEX VOL. 76 (1980) SODIUM Absorption, circular dichroism and magnetic circular dichroism spectra of trisodium praseodymium tris(oxydiacetate) di(sodium perchlorate) hexahydrate, 620-32 Ultrasonic relaxation of surfactants in water and deuterium oxide solutions, 794-802 Helium I and helium I1 photoelectron spectra of alkali fluorides in the vapor phase, 1523-32 Ultrasonic relaxation studies of sodium octyl sulfate complexes with synthetic polymers and a protein in aqueous solution, 1535-42 SOFT Molecular dynamics simulation of a soft-disk system, 1646-54 SOLID Thinning and rupture of ring-shaped films, 250-66 Cluster model for solids, 520-33 SOLN Polarizable acid-water hydrogen bonds with aqueous solutions of carboxylic acids, 14-25 Distribution of ions in electrolyte solutions and plasmas.Part 1, 1093-102 Ultrasonic relaxation studies of sodium octyl sulfate complexes with synthetic polymers and a protein in aqueous solution, 1535-42 Distribution of ions in electrolyte solutions and plasmas.Part 2, 1599-609 SOLUTE Far infrared solution spectra. Volume of rotation and effective torque, 286-301 SOLVATION Analysis of the vibrational spectrum of symmetrically solvated alkali metal cations, 979-1007 Vibrational spectrum of alkali metal cations in distorted solvation shells. A prediction, 1008-25 Dynamic solvation. Ionic vibrations in nonstationary solvation shells, 1026-44 Transition state model for water exchange in the first solvation shell of hydrated cations according to quantum chemical calculations, 1268-74 Solvation forces in molecular fluids, 1478-84 SOLVENT Nonlocal screening in a polar solvent, 67-8 1 Dielectric study of the rotational equilibriums of succinonitrile, 197-204 Study of solvation models.Interpretation of solvent effect on the R* <-n transition of methyl acetate, 490-5 Solvent structure in particle interactions. Low pressure effects and analytic limits, 776-84 Thermodynamicsof poly(dimethylsi1oxane) solutions, 895-904 Viscosity dependent internal conversion in the rhodamine dye, Fast Acid Violet 2R, 1627-37 Internal conversion in the rhodamine dye, Fast Acid Violet 2R, 1638-45 SOUND Evaluation of the van der Waals constant, internal pressure, and sound velocity in binary liquid mixtures from Flory’s theory, 121 5-1 8 SPACE Cluster groups, 53441 SPECTRA Luminescence and 4A2+ 2E,2T1 absorption spectrum of hexaureachromium(II1) iodide and hexaureaalu- minum(II1) iodide :hexaureachromium(III), 82-7 Nonrigid molecules.Part 4. Hydrogen atom scrambling in the mass spectra of hydrocarbons, 88-95 Optical properties of [M(L-L)2M(L-L)2X2](ClO4)4, (M = platinum, palladium; L-L = 1,24iaminoeth-ane or 1,2-diaminopropane; X = chlorine, bromine, iodine): bulk and small particles, 104-1 1 Photoelectron spectra of selenium dichloride and diselenium dichloride, 148-52 Electronic structure and valence ionization energies of trichlorooxochromium studied by ab initio and SW-Xa methods, 164-71 Kinetic spectroscopy in the far vacuum ultraviolet. Part 5. Oscillator strengths for the 3s, 4s, 5s, 3d and 4d 4P~-2p3 4S03.2 transitions in atomic nitrogen, 369-82 Microwave spectrum and conformation of triformylmethane, 383-90 Absorption, circular dichroism and magnetic circular dichroism spectra of trisodium praseodymium tris(oxydiacetate) di(sodium perchlorate) hexahydrate, 620-32 Emission spectra of the cations of cyanodiacetylene, methylcyanodiacetylene and ethylcyanodiacetylene in the gaseous phase.-A(rl) --+-X(rl) band systems, 676-84 Kinetics and photochemistry of the nitrate radical. Part 1. Absolute absorption cross section, 785-93 Photoelectron spectra of nitrosomethane, tert-nitrosobutane and some perhalonitrosomethanes, 844-59 Low-frequency bending motions of the silyl pseudohalides SiH3NCY (Y = 0,S, Se). An experimentaland theoretical study, 860-71 Analysis of the vibrational spectrum of symmetrically solvated alkali metal cations, 979-1007 Vibrational spectrum of alkali metal cations in distorted solvation shells.A prediction, 1008-25 Ionic and neutral optical emissions induced by helium(1a) excitation of nitriles, 1079-83 Resonance Raman, infrared, and electronic spectral studies of p-oxo-decahalodimetallate speciesosmium, rhenium, ruthenium, and tungsten, 1103-18 Microwave spectrum of acetyl isocyanate, 1208-1 3 Molecular structure of 1,2-dirnethyl-l,2-diazetidine. Electron diffraction and microwave study and normal coordinate analysis, 1293-303 J.C.S. FARADAY I1 SUBJECT INDEX VOL. 76 (1980) SPECTRA(contd)The 4Azg <-> 2E, transitions in trans-dichlorobis(ethylenediamine)chromium( 1+) and trans- dichlorobis(1,3-diarninopropane)chromium( 1+), 138 1-7 Charge-exchange mass spectra of ethyl acetate, methyl propionate, and propyl formate, 1450-7 Charge-xchange mass spectra of thiophene, pyrrole, and furan, 15 16-22 Attempted photoproduction of hydrogen using sulfophthalocyanines as chromophores for three- component systems, 1618-26 Viscosity dependent internal conversion in the rhodamine dye, Fast Acid Violet 2R, 1627-37 SPECTROSCOPY Power reflection spectroscopy near the Brewster angle. Molecular dynamics of liquids, 1 147-60 SPHERE Ion-pairing in aqueous media. An exact solution for the interaction energy associated with two dielectric spheres, 575-88 Statistical geometry of hard-sphere systems, 693-703 Hard-sphere model of fused salts, 1347-53 SPIN Nuclear magnetic resonance spin-lattice relaxation and barriers in ethylenediammonium chloride, bromide, iodide, and sulfate, 1196-207 SPLITTING Vibrational spectrum of alkali metal cations in distorted solvation shells.A prediction, 1008-25 Further study of the beryllium monohydride radical by UHF-type and configuration interaction methods, 1655-63 STARK Microwave spectra of bromotrifluoromethane and iodotrifluoromethane. Structures and dipole moments 339-50 STATE Kinetics of excited states of bromine using laser excitation. Part 2. Radiative lifetime and collisional deactivation of the B3ll(O+,) state, 405-19 Statistical geometry of hard-sphere systems, 693-703 Volume relaxation in simple liquids, 704-10 STATISTIC Statistical geometry of hard-sphere systems, 693-703 STILBENE Lowest excited states of aza-analogs of stilbene.INDO/S calculation, 598-605 STRENGTH Kinetic spectroscopy in the far vacuum ultraviolet. Part 5. Oscillator strengths for the 3s, 4s, 5s, 3d and 4d 4P~-2p3 4S03.2 transitions in atomic nitrogen, 369-82 Ion-pairing in aqueous media. An exact solution for the interaction energy associated with two dielectric spheres, 575-88 Lowest excited states of aza-analogs of stilbene. INDO/S calculation, 598-605 Some model potentials for the ammoniated electron, 1592-8 STRONG Theory of transient response for arbitrarily strong driving fields, 542-9 STYRYL Lowest excited states of aza-analogs of stilbene. INDO/S calculation, 598-605 STYRYLPYRIDINE Lowest excited states of aza-analogs of stilbene. INDO/S calculation, 598-605 SUCCINONITRILE Dielectric study of the rotational equilibriums of succinonitrile, 197-204 SULFATE SCF-Xu investigation of the ionization energies of perchlorate, sulfate, and phosphate anions, 441-5 Ultrasonic relaxation of surfactants in water and deuterium oxide solutions, 794-802 Nuclear magnetic resonance spin-lattice relaxation and barriers in ethylenediammonium chloride, bromide, iodide, and sulfate, 1196-207 Ultrasonic relaxation studies of sodium octyl sulfate complexes with synthetic polymers and a protein in aqueous solution, 153542 SULFIDE Kinetic study of the reactions of hydrogen and deuterium atoms with hydrogen bromide and deuterium bromide by time-resolved resonance fluorescence, 276-85 Depolarized light scattering from gases of anisotropic molecules at intermediate pressures, 309-1 5 Energy disposal in the vacuum ultraviolet photodissociation of carbon disulfide and carbon diselenide, 905-14 Energy transfer from state-selected photofragments.Electronic quenching of CS(Alll),y~5,915-22 Reactions of carbon dioxide, carbon dioxide dimer, and water cations with various neutral molecules, 1084-92 Quadrupole moment and magnetic anisotropy of carbon disulfide, 1245-8 Vibrational energy transfer from carbon monoxide (v = I), nitrogen (v = 1) carbon dioxide(001), nitrous oxide(001), and carbonyl sulfide(001) to ozone, 1354-70 J.C.S. FARADAY I1 SUBJECT INDEX VOL. 76 (1980) SULFO Attempted photoproduction of hydrogen using sulfophthalocyanines as chromophores for three- component systems, 16 18-26 SULFOPHTHALOCYANINE Attempted photoproduction of hydrogen using sulfophthalocyanines as chromophores for three- component systems, 161 8-26 SULFOPHTHOCYANINE Attempted photoproduction of hydrogen using sulfophthalocyanines as chromophores for three- component systems, 1618-26 SULFUR Reactions of carbon dioxide, carbon dioxide dimer, and water cations with various neutral molecules, 1084-92 SUPERSATD Condensation modeling for highiy supersaturated vapors: application to iron, 1494-5 1 5 SURFACE Oxidation of polycrystalline and (1 11) lead surfaces studied by electron spectroscopy, 267-75 Electronic transitions at the surface of potassium iodide microcrystals.Part 1. Surface states, 420-30 A test of a two-density theory of surface tension, 936-47 SURFACTANT Ultrasonic relaxation of surfactants in water and deuterium oxide solutions, 794-802 Thermodynamic approach to the interpretation of electrokinetic data near the isoelectric point, 1254-67 Ultrasonic relaxation studies of sodium octyl sulfate complexes with synthetic polymers and a protein in aqueous solution, 1535-42 SUSCEPTIBILITY Magnetic susceptibility of expanded liquid selenium, 756-60 Influence of the nonmagnetic cation upon the sign of the chromium(III)chromium(III) coupling in trirutile compounds MCr206 (M =Te, W), 1224-33 SYMMETRY Polarizable acid-water hydrogen bonds with aqueous solutions of carboxylic acids, 14-25 Cluster groups, 534-41 SYSTEM Statistical geometry of hard-sphere systems, 693-703 Determination of partial molar quantities in multicomponent systems, 1 1 19-27 Statistical thermodynamics of fluid phase equilibrium in a conformal polydisperse system, 1458-67 Phase separation in a polydisperse system, 1468-77 TELLURIUM Influence of the nonmagnetic cation upon the sign of the chromium(III)-chromium(III) coupling in trirutile compounds MCr206 (M =Te, W), 1224-33 TEMP Volume relaxation in simple liquids, 704-10 TENSION A test of a two-density theory of surface tension, 936-47 Marangoni instability at a spherical interface.Breakdown of fluid drops at low surface tension and cytokinetic phenomena in the living cell, 1170-95 TETRACHLOROMETHANE Magnetic birefringence in liquids of near-isotropic molecules, 1610-1 7 TETRAFLUOROGERMANE SCF-Xa study of the electronic structure of tetrahalomethanes, tetrahalosilanes, and tetrafluorogermane 1375-80 TETRAHALOMETHANE SCF-Xa study of the electronic structure of tetrahalomethanes, tetrahalosilanes, and tetrafluorogermane 1375-80 TETRAHALOSILANE SCF-Xa study of the electronic structure of tetrahalomethanes, tetrahalosilanes, and tetrafluorogermane 1375-80 TETRAMETHYL Magnetic birefringence in liquids of near-isotropic molecules, 1610-1 7 TETRAMETHY LTIN Magnetic birefringence in liquids of near-isotropic molecules, 1610-17 TETRAPHENYL On the NH proton tunneling rate in meso-tetraphenylporphine, 729-3 1 TETRAPHENYLPORPHINE On the NH proton tunneling rate in meso-tetraphenylporphine, 729-3 1 THEOR Pulsed source thermal lens.Part 1. Theoretical analysis. 633-47-. THEORY Far infrared solution spectra. Volume of rotation and effective torque, 286-301 Theory of cooperative phenomena in monolayers of hydroxyhexadecanoic acid isomers, 43 1-40 42 J.C.S. FARADAY I1 SUBJECT INDEX VOL. 76 (1980) Non-Gaussian, non-Markov processes, 761-6 A test of a two-density theory of surface tension, 936-47 Thermodynamic approach to the interpretation of electrokinetic data near the isoelectric point, 1254-67 Theory of the electric double layer using a modified Poisson-Boltzmann equation, 1388-408 THERMODN Vibrational spectra of matrix isolated aluminum chloride dimer. Isotopic fine structure and valence force field, 26-41 Study of self-association of tert-butyl alcohol by linear and nonlinear dielectric effects, 42-8 Atomization energies of complex gaseous yttrium carbides, 10 1-3 Infrared studies and thermodynamics of hydrogen bonding in 2-chloroethanol,3-chloropropanoland 4-chlorobutanol, 233-49 Atomization energies of the molecules LiSiO(g) and Si202(g) by mass spectrometric gaseous equilibriums 447-52 Thermodynamics of poly(dimethylsi1oxane) solutions, 895-904 Thermodynamic approach to the interpretation of electrokinetic data near the isoelectric point, 1254-67 Molecular dynamics simulation of a soft-disk system, 1646-54 THIOPHENE Charge-exchange mass spectra of thiophene, pyrrole, and furan, 15 16-22 TIME Transport properties in dilute gases: an approach using time-correlation functions.Part 1. Viscosity and thermal conductivity of gases and gas mixtures in which the exchange of molecular internal energy is slow, 735-46 Transport properties in dilute gases: an approach using time-correlation functions. Part 2. Viscosity and thermal conductivity of gases and gas mixtures in which the exchange of molecular internal energy is significant, 747-5 5 TIN Structure and fluxional behavior of the adducts of orthoquinones with organotin halides. An electron spin resonance study, 948-53 Magnetic birefringence in liquids of near-isotropic molecules, 1610-1 7 TOLUENE Electron spin resonance studies of ion association. Part 8. Effects of ion-pairing on nitrogen-14 hyperfine splittings in psubstituted nitrobenzene anions, 822-6 TORQUE Far infrared solution spectra.Volume of rotation and effective torque, 286-301 TRANSFER Mechanisms of singlet energy transfer in doped anthracene crystals at 5 K, studied by nanosecond spectrofluorimetry, 472-89 Role of intermolecular forces in proton-transfer reactions, 954-60 Laser-excitation studies of bromine. Collisional energy transfer involving resolved quantum states of excited Br2B3lI(Ou+), 961-78 Vibrational spectrum of alkali metal cations in distorted solvation shells. A prediction, 1008-25 Reactions of carbon dioxide, carbon dioxide dimer, and water cations with various neutral molecules, 1084-92 Theory of the kinetic isotope effect in proton transfer reactions in a polar medium, 1128-46 Magnetooptical studies of liquid mixtures.Part 4. Additivity of the Faraday effect, the magnetic rotation dispersion constant, and the excess magnetic rotation in binary liquid mixtures, 132&35 Vibrational energy transfer from carbon monoxide (v = l), nitrogen (v = 1) carbon dioxide(001), nitrous oxide(001), and carbonyl sulfide(001) to ozone, 1354-70 Laser-induced fluorescence studies: the B-X transition of chlorine. Part 6. Rotationally-dependent predissociation, 1561-8 Quantum-resolved dynamics of excited states. Part 6. Radiative lifetime and collisional deactivation rates in bromine fluoride (B), 1569-85 TRANSITION Positron lifetime study of the transition from glassy to normal liquid state for two phenyl ethers, 225-32 Kinetic spectroscopy in the far vacuum ultraviolet. Part 5.Oscillator strengths for the 3s, 4.9, 5s, 3d and 4d 4PJ-2p3 4S03.2 transitions in atomic nitrogen, 369-82 Photoelectron spectra and electronic structure of the transition metal dichlorides, MC12 (M = chromium, manganese, iron, cobalt, nickel), 506-19 Absorption, circular dichroism and magnetic circular dichroism spectra of trisodium praseodymium tris(0xydiacetate) di(sodium perchlorate) hexahydrate, 620-32 Heat capacity of bis(adiponitrile)copper(I) nitrate. An order-disorder transition in a dilute system of nitrate ions, 803-1 1 Energy disposal in the vacuum ultraviolet photodissociation of carbon disulfide and carbon diselenide, 905-14 Study of the semiconductor-to-metal transition in vanadium dioxide and vanadium sesquioxide by ultraviolet photoelectron spectroscopy, 929-3 5 Laser-induced fluorescence studies: the EX transition of chlorine.Part 5. Radiative lifetime of the B state, 1275-92 J.C.S. FARADAY I1 SUBJECT INDEX VOL. 76 (1980) TRANSITION(contd)Statistical thermodynamics of fluid phase equilibrium in a conformal polydisperse system, 1458-67 Laser-induced fluorescence studies: the B-X transition of chlorine. Part 6. Rotationally-dependentpredissociation, 1561-8 Molecular dynamics simulation of a soft-disk system, 1646-54 TRANSPORT Transport properties in dilute gases: an approach using time-correlation functions. Part 1. Viscosity and thermal conductivity of gases and gas mixtures in which the exchange of molecular internal energy is slow, 735-46 Transport properties in dilute gases: an approach using time-correlation functions.Part 2. Viscosity and thermal conductivity of gases and gas mixtures in which the exchange of molecular internal energy is significant, 747-55 TRIAT Non-Gaussian, non-Markov processes, 761-6 TRICLINIC Structure and dynamics of a new phase of anthracene, 1336-46 TRIETHYLAMINE Photodimerization of benzyl9-anthroate in the presence of triethylamine. Role of exciplex and triplet formation, 1-1 3 TRIETHYLENE Carbon-1 3 and nitrogen-1 4 nuclear magnetic resonance study of triethylenediamine, 57 1-3 TRIETHYLENEDIAMINE Carbon-1 3 and nitrogen-14 nuclear magnetic resonance study of triethylenediamine, 57 1-3 TRIFORMYLMETHANE Microwave spectrum and conformation of triformylmethane, 38390 TRIRUTILE Influence of the nonmagnetic cation upon the sign of the chromium(III~hromium(II1)coupling in trirutile compounds MCr206 (M = Te, W), 1224-33 TUNGSTATE Vibrational structure in the luminescence spectra of uraniumdoped tungstates with ordered perovskite structure, 872-84 Resonance Raman, infrared, and electronic spectral studies of p-oxe-decahalodimetallate speciesosmium, rhenium, ruthenium, and tungsten, 1103-18 TUNGSTEN Influence of the nonmagnetic cation upon the sign of the chromium(III~hromium(III)coupling in trirutile compounds MCr206 (M = Te, W), 1224-33 TUNNELING On the NH proton tunneling rate in meso-tetraphenylporphine, 729-3 1 Role of intermolecular forces in proton-transfer reactions, 954-60 UHF Further study of the beryllium monohydride radical by UHF-type and configuration interaction methods, 1655-63 ULTRASONIC Ultrasonic relaxation of surfactants in water and deuterium oxide solutions, 794-802 ULTRASOUND Ultrasonic relaxation studies of sodium octyl sulfate complexes with synthetic polymers and a protein in aqueous solution, 1535-42 UPS Photoelectron spectra and electronic structure of the transition metal dichlorides, MC12 (M = chromium, manganese, iron, cobalt, nickel), 506-19 High resolution ultraviolet photoelectron spectra of monohalo- and p-dihalobenzenes, 556-70 Electronic structure and assignment of the ultraviolet photoelectron spectra of 6-methyl-2-0x0-pyridine complexes of dichromium(I1) and dimolybdenum(II), 885-94 Study of the semiconductor-to-metal transition in vanadium dioxide and vanadium sesquioxide by ultraviolet photoelectron spectroscopy, 929-35 Photoelectron spectra and valence shell electronic structure of zinc and cadmium difluoride, 13 14-23 Helium I and helium I1 photoelectron spectra of alkali fluorides in the vapor phase, 1523-32 Study by high-temperature photoelectron spectroscopy of the electronic structure of the transition metal difluorides, cupric fluoride and zinc fluoride, 1672-82 URANIUM Vibrational structure in the luminescence spectra of uranium-doped tungstates with ordered perovskite structure, 872-84 UREA Luminescence and 4Ae 2E,2T1 absorption spectrum of hexaureachromium(II1) iodide and hexaureaalu- minum(II1) iodide :hexaureachromium(III), 82-7 uv Luminescence and 4A2-3 2E,2T1 absorption spectrum of hexaureachromium(II1) iodide and hexaureaalu- minum(II1) iodide :hexaureachromium(III), 82-7 Kinetic spectroscopy in the far vacuum ultraviolet.Part 5. Oscillator strengths for the 3s, 4s, 5s, 3d and 44 J.C.S. FARADAY IT SUBJECT INDEX VOL. 76 (1980) UV(con td) 4d 4P~-2p3 4S03.2 transitions in atomic nitrogen, 369-82 Electronic transitions at the surface of potassium iodide microcrystals. Part 1. Surface states, 420-30 Study of solvation models. Interpretation of solvent effect on the 7t* <-n transition of methyl acetate, 490-5 Kinetic study of ground state atomic nitrogen, N(24S3.2), by time-resolved atomic resonance fluorescence 60619 Absorption, circular dichroism and magnetic circular dichroism spectra of trisodium praseodymium tris(0xydiacetate) di(sodium perchlorate) hexahydrate, 620-32 Emission spectra of the cations of cyanodiacetylene, methylcyanodiacetylene and ethylcyanodiacetylene in the gaseous phase.-A(d) +X(d) band systems, 676-84 Kinetics and photochemistry of the nitrate radical. Part 1. Absolute absorption cross section, 785-93 Energy disposal in the vacuum ultraviolet photodissociation of carbon disulfide and carbon diselenide, 905-14 Vibrational spectrum of alkali metal cations in distorted solvation shells. A prediction, 1008-25 Ionic and neutral optical emissions induced by helium(1ol) excitation of nitriles, 1079-83 The 4A2, <-> 2E, transitions in trans-dichlorobis(ethylenediamine)chromium( 1+) and trans- dichlorobis(1,3diaminopropane)chromium( 1 +), 138 1-7 Viscosity dependent internal conversion in the rhodamine dye, Fast Acid Violet 2R, 1627-37 VALENCE Photoelectron spectra and valence shell electronic structure of zinc and cadmium difluoride, 13 14-23 VAN Evaluation of the van der Waals constant, internal pressure, and sound velocity in binary liquid mixtures from Flory’s theory, 1215-18 VANADIUM Study of the semiconductor-to-metal transition in vanadium dioxide and vanadium sesquioxide by ultraviolet photoelectron spectroscopy, 929-35 VAPOR Prediction of phase equilibriums using the Redlich-Kwong equation of state, 1045-9 Condensation modeling for highly supersaturated vapors: application to iron, 1494-5 15 Helium I and helium I1 photoelectron spectra of alkali fluorides in the vapor phase, 1523-32 VELOCITY Evaluation of the van der Waals constant, internal pressure, and sound velocity in binary liquid mixtures from Flory’s theory, 12 15-1 8 VIBRATION High resolution ultraviolet photoelectron spectra of monohab and p-dihalobenzenes, 556-70 Emission spectra of the cations of cyanodiacetylene, methylcyanodiacetylene and ethylcyanodiacetylene in the gaseous phase.-A(d) +-X(d) band systems, 676-84 Vibrational relaxation of excited oxygen 02(lA&, studied with a discharge-flow-shock-tube technique,923-8 Laser-excitation studies of bromine. Collisional energy transfer involving resolved quantum states of excited Br2B3II(OU+), 961-78 Dynamic solvation.Ionic vibrations in nonstationary solvation shells, 1026-44 Theory of the kinetic isotope effect in proton transfer reactions in a polar medium, 1128-46 A study of three dimol emissions of singlet oxygen, 02(1A ,using a discharge flow shock tube, 1442-9 Quantum-resolved dynamics of excited states. Part 6. Ra diative lifetime and collisional deactivation rates in bromine fluoride (B), 1569-85 VIBRATIONAL Energy disposal in the vacuum ultraviolet photodissociation of carbon disulfide and carbon diselenide, 905-14 Analysis of the vibrational spectrum of symmetrically solvated alkali metal cations, 979-1007 Vibrational energy transfer from carbon monoxide (v = l), nitrogen (v = 1) carbon dioxide(001), nitrous oxide(001), and carbonyl sulfide(001) to ozone, 1354-70 VIOLET Viscosity dependent internal conversion in the rhodamine dye, Fast Acid Violet 2R, 1627-37 Internal conversion in the rhodamine dye, Fast Acid Violet 2R, 163845 VIOLOGEN Attempted photoproduction of hydrogen using sulfophthalocyanines as chromophores for three- component systems, 1618-26 VIRIAL Fifth virial coefficient for the Lennard-Jones fluid in two dimensions.Integral equation results, 8 12-21 VISCOELASTIC Viscous, viscoelastic and dielectric properties of a perfluorinated polymer, Krytox 143-AB, 205-1 6 VISCOSITY Volume relaxation in simple liquids, 704-10 Transport properties in dilute gases: an approach using time-correlation functions.Part 1. Viscosity and thermal conductivity of gases and gas mixtures in which the exchange of molecular internal energy is slow, 735-46 Transport properties in dilute gases: an approach using time-correlation functions. Part 2. Viscosity and J.C.S. FARADAY I1 SUBJECT INDEX VOL. 76 (1980) VISCOSITY(contd)thermal conductivity of gases and gas mixtures in which the exchange of molecular internal energy is significant,747-55 Hard-sphere model of fused salts, 1347-53 Viscosity dependent internal conversion in the rhodamine dye, Fast Acid Violet 2R, 1627-37 VISIBLE Vibrational spectrum of alkali metal cations in distorted solvation shells. A prediction, 1008-25 VOL Volume relaxation in simple liquids, 704- 10 Thermodynamics of poly(dimethylsi1oxane) solutions, 895-904 WAALS Evaluation of the van der Waals constant, internal pressure, and sound velocity in binary liquid mixtures from Flory’s theory, 1215-18 WATER Electron paramagnetic resonance and nuclear magnetic resonance studies of lipid-water systems, 96-1 00 Infrared investigation of water structure in desalination membranes, 13647 Cusped-Gaussian molecular wave functions.Part 3. Basis sets for the first-row atoms, 391-404 Light scattering study of the diffusion of interacting particles, 767-75 Reactions of carbon dioxide, carbon dioxide dimer, and water cations with various neutral molecules, 1084-92 Transition state model for water exchange in the first solvation shell of hydrated cations according to quantum chemical calculations, 1268-74 WAVE Cusped-Gaussian molecular wave functions.Part 3. Basis sets for the first-row atoms, 391-404 XENON Energy transfer from state-selected photofragments. Electronic quenching of CS(AlII)Vw5, 91 5-22 XYLENE Evaluation of the van der Waals constant, internal pressure, and sound velocity in hinary liquid mixtures from Florv’s theorv. 1215-18 XYLIL <, Influence of screening of intramolecular easily polarizable hydrogen bonds on their infrared absorbance, 1061-6 XY LILDIAMINE Influence of screening of intramolecular easily polarizable hydrogen bonds on their infrared absorbance, 1061-6 YEVICK Solvent structure in particle interactions. Low pressure effects and analytic limits, 776-84 Fifth virial coefficient for the Lennard-Jones fluid in two dimensions.Integral equation results, 812-21 YTTRIUM Atomization energies of complex gaseous yttrium carbides, 10 1-3 ZEEMAN Absorption, circular dichroism and magnetic circular dichroism spectra of trisodium praseodymium tris(oxydiacetate) di(sodium perchlorate) hexahydrate, 620-32 Zeeman effect of chlorine nuclear quadrupole resonance and hydrogen bonding in 2,6-, 2,5-, and 33-dichlorophenols, 1055-60 ZETA Thermodynamic approach to the interpretation of electrokinetic data near the isoelectric point, 1254-67 ZINC Photoelectron spectra and valence shell electronic structure of zinc and cadmium difluoride, 1314-23 Attempted photoproduction of hydrogen using sulfophthalocyanines as chromophores for three- component systems, 161 8-26 Study by high-temperature photoelectron spectroscopy of the electronic structure of the transition metal difluorides, cupric fluoride and zinc fluoride, 1672-82 INSTRUCTIONS TO AUTHORS General Policy The Journal of the Chemical Society is a medium for reporting selected original and significant contributions to new chemical knowledge.Articles which do not advance knowledge (e.g. reviews) will not normally be considered for publication in the Journal. All contributions are judged in the criteria of (i) originality and quality of scientific content and (ii) appropriateness of the length to content of new science. Thus, papers reporting results which would be routinely predicted or result from application of standard procedures or techniques are unlikely to prove acceptable in the absence of other attributes which themselves make publication desirable.Although short articles are acceptable, the Society strongly discourages fragmentation of a substantial body of work into a number of short publications. Unnecessary fragmentation will be a valid reason for rejection of manuscripts. The Journal is published in five Transactions: Dalton: Inorganic, Perkin I: Organic and Bio-organic; Faraday I: Physical; Perkin 11: Physical Organic; Faraday 11: Chemical Physics Authors are requested to indicate, at the time they submit a typescript, the Transactions for which it is intended. Should this seem unsuitable, the Editor will inform the author.Conditions Governing Acceptance Contributions which have appeared or have been accepted for publication with essentially the same content in another journal or which incorporate freely available printed work will not be published in the Journal except by permission of the Council. This restriction does not apply to results previously published in materially abbreviated form, as a paper presented at a symposium, as a communication to Chemical Communications, as a letter to the Editor of other periodicals, or as a patent. Contributions are accepted by the Society on the understanding that the authors (a) have obtained any necessary authority for publication, and (b) will, if requested, surrender their copyright to the Society. Authors are solely responsible for the factual accuracy of their contributions.Since the Society reserves the right to retain all typescripts sent to it, authors are advised to keep copies. When contributions have been submitted for publication the authors are not at liberty, save by permission of the Society, to withdraw or delay them or to publish them elsewhere until after publication by the Society.* Submission of Articles Typescripts should be addressed to: The Director of Publications, The Royal Society of Chemistry, Burlington House, London W1V OBN. Three copies of the typescript (a top copy and two good quality carbon or Xerox copies) are required. Rapid publication is aided by careful preparation of text and illustrations and strict adherence to the format and conventions of individual Transactions; detailed Instructions to Authors are available on request from the Editor.Particular attention is drawn to the use of (i) SI units and associated conventions, (ii) IUPAC nomenclature for compounds, and (iii) standard methods of literature citation. Administration Receipt of a contribution for consideration will be acknowledged immediately by the Editorial Office. The acknowledgement will indicate the paper reference number assigned to the con- tribution. Authors are particularly asked to quote it on all subsequent correspondence. Reprints Although 50 free reprints are provided free for each paper a further order may be made on the order form sent to the authors with the proofs.*Attention is drawn to the Society’s Bye-Law, 85. NOTES It has always been the policy of the Faraday Transactions that brevity should not be a factor influencing acceptability for publication. In addition however to full papers both sections carry at the end of each issue a section headed ‘Notes’, which are short self-contained ac- counts of experimental observations, results, or theory that will not require enlargement into ‘full’ papers. The ‘Notes’ section is not used for preliminary communications. The layout of a ‘Note’ is the same as that of a paper. Short summaries are required. The procedure for submission, administration, refereeing, editing and publication of ‘Notes’ is the same as for ‘full’ papers. However, ‘Notes’ are published more quickly than papers since their brevity facilitates processing at all stages.The Editors endeavour to meet authors’ wishes as to whether an article is a full paper or a ‘Note’, but since there is no sharp dividing line between the one and the other, either irrterms of length or character of contents, the right is retained to transfer overlong ‘Notes’ to the ‘full papers’ section. As a guide a ‘Note’ should not exceed 1500 words or word-equivalents. Nomenclature and Symbolism For many years the Society has actively encouraged the use of standard IUPAC nomenclature and symbolism in its publications as an aid to the accurate and unambiguous communication of chemical information between authors and readers. In order to encourage authors to use IUPAC nomenclature rules when drafting papers, attention is drawn to the following publi- cations in which both rules themselves and guidance on their use are given.Physicochemical Quantities and Units Manual of Symbols and Terminology for Physicochemical Quantities and Units. (Pure and Appl. Chem., Vol. 51, No. 1, 1979, pp. 141. Also available as a soft-cover booklet from Pergamon Press, Oxford.) Surface Chemistry ‘Definitions, Terminology, and Symbols in Colloid and Surface Chemistry -I.’ (Pure and Appl. Chem., Vol. 31, No. 4, 1972, pp. 577-638.) ‘Definitions, Terminology, and Symbols in Colloid and Surface Chemistry -11. Heterogen- eous Catalysts.’ (Pure and Appl. Chem., Vol. 46, No. 1, 1976, pp. 71-90.) -In addition, the terminology and symbols for the following subject areas are available either in the form of soft-cover booklets from Pergamon Press (denoted by *) or have been the subject of articles in Pure and Applied Chemistry in recent years: activities;* chromatography; electrochemistry; electron spectroscopy; equilibria, fluid flow; ion exchange; liquid-liquid dis- tribution; molecular force constants; Mossbauer spectra; nuclear chemistry; pH; polymers; quantum chemistry; radiation;* Raman spectra; reference materials (recommended reference materials for the realisation of physicochemical properties: general introduction, enthalpy, optical rotation, surface tension, optical refraction, molecular weight, absorbance and wavelength, pressure-volume-temperature relationships, reflectance, potentiometric ion activ- ities, testing distillation columns), solution chemistry; spectrochemical analysis; surface chemistry; thermodynamics, and zeolites.Finally, the rules for the naming of organic and inorganic compounds are dealt with in the following publications from Pergamon Press: ‘Nomenclature of Organic Chemistry, Sections A, B, C, D, E, F, and H’, 1979. ‘Nomenclature of Inorganic Chemistry’, 1971. Publication of Theoretical and Computational Papers The Journals Committee has considered its policy towards the publication of papers with a heavily computational content, particularly where these involve standard methods, such as semi-empirical or ab initio calculations of molecular electronic properties using readily available computer programs.Many such papers report what would be considered ‘routine work’ in other areas of chemistry and have often included extensive detail. A specialist sub-committee formulated a set of proposals which circulated to a large repre- sentative sample of theoretical chemists and met with general acceptance. These, with the comments on them, form the basis of this notice. The Journals Committee recognises that computational work can play a valuable role in chemistry, and will continue to do so on an increasing scale. It accepts the time-honoured principle that the first criterion for publication of a paper by the Society should be the worthiness of the chemical problem considered, rather than the particular techniques em- ployed by the author.For example, the use of a new computing algorithm, or the modification of a program, would not usually, on its own, provide sufficient justification for publication. The Journals Committee recommends to authors the following guidelines for the prepara- tion of computational papers, so that the material can be presented concisely and effectively. (i) Papers should be submitted to the appropriate journal: a paper containing innovations in theory to Faraday Transactions 11, one in which the computations are incidental to the chemistry to Perkin, Dalton or Faraday I Transactions. Papers concerned mainly with computational details are unlikely to be accepted. (ii) The purpose of the paper and the precise objectives of the calculations performed should be clearly stated: the results obtained should be reported only in so far as they relate to those objectives. (iii) Many papers use a routine procedure based on a well documented method, be it semi- empirical or ab initio.It is then sufficient to name the particular variant, referring to key papers in which the method was developed, to cite the computer program used, and to indicate briefly any modification made by the author. A review of theoretical background would be out of place, but an author should say why he considers the method adequate for his purposes. (iv) Extensive tabulation of numerical results, such as the magnitudes of atomic orbital coefficients, electron populations, contour maps of molecular orbitals and electron densities, and peripheral material of a similar nature, is normally unnecessary.Lengthy line-by-line discussion of such material is, as a general rule, quite unacceptable. Where an author considers that there is a special need to make such material available to other workers, as with highly accurate computations, for example, then this may be deposited with the British Library as a Supplementary Publication. Such ma_terial should be submitted with the main paper, clearly distinguished from it, and referred to in the main text. Guidelines can never provide sufficient criteria for acceptance or rejection of a paper. Critical assessment of the theoretical methods used in a computation, and of their suitability for the purpose in hand, will continue to be entrusted to specialist referees who must also decide whether the results are new and advance science.Deposition of Data-Supplementary Publications Scheme Preamble The growing volume of research that produces large quantities of data, the increasing facilities for analysing such data mechanically, and the rising cost of printing are each making it very difficult to publish in the Journal in the normal way the full details of the experimental data which become available. Moreover, whilst there is a large audience for the general method and conclusions of a research project, the number of scientists interested in the details, and in particular in the data, of any particular case may be quite small. The British Library Lending Division (B.L.L.D.) in consultation with the Editors of scientific journals, has now developed a scheme whereby such data and detail may be stored and then copies made available on request at the B.L.L.D., Boston Spa.The Society is a sponsor of this scheme and has in- dicated to the B.L.L.D. its wish to use the facilities being made available in this ‘Supplemen- tary Publications Scheme’. Bulk information (such as crystallographic structure factor tables, computer programmes and output, evidence for amino-acid sequences, spectra, etc.), which accompany papers pub- lished in future issues of the Society’s Journal may in future be deposited, free of charge, with the Supplementary Publications Scheme, either at the request of the author and with the approval of the referees or on the recommendation of referees and the approval of the author.The Scheme Under this scheme, authors will submit articles and the supplementary material to the Journal simultaneously in the normal way, and both will be refereed. If the paper is accepted for publication the supplementary material will be sent by the Society to the B.L.L.D. where it will be stored. Copies will be obtainable by individuals both in the U.K. and abroad on quoting a supplementary publication number that will appear in the parent article. Preparation of Material Authors will be responsible for the preparation of camera-ready copy according to the follow- ing specifications (although the Society will be prepared to help in case of difficulty). (a) Optimum page size for text or tables in typescript: up to 30 cm x 21 cq. (b) Limiting page size for text or tables in typescript: 33 cm x 24 cm. (c) Limiting size for diagrams, graphs, spectra, etc.: 39 cm x 28-5 cm. (d) Tabular matter should be headed descriptively on the first page, with column headings recurring on each page. (e) Pages should be clearly numbered. It is recommended that all material which is to be deposited should be accompanied by some prefatory text. Normally this will be the summary from the parent paper and authors will greatly aid the deposition of the material if a duplicate copy of the summary is provided. If authors have the facilities available the use of a type face designed to be read by computers is encouraged. Deposition The Society will be responsible for the deposition of the material with the B.L.L.D. The B.L.L.D. will not receive material direct from authors since the Library wishes to ensure that the material had been properly and adequately refereed. Action by the Society The Society will receive a manuscript for publication together with any supplementary material for deposition and will circulate all of this to referees in the normal way. When the edited manuscript is sent to the printers the supplementary material will be sent for deposition to the B.L.L.D. who will issue the necessary publication number. The Society will add to the paper, at the galley proof stage, a footnote indicating what material has been deposited in the Supplementary Publications Scheme, the number of pages it occupies, the supplementary publication number, and details as to how copies may be obtained. Availability Copies of Supplementary Publications may be obtained from the B.L.L.D. on demand by organisations which are registered borrowers. They should use the normal forms and coupons for such requests addressing them as follows: Mr. J. P. Chillag, British Library Lending Division, Boston Spa, We therby , West Yorkshire, LS23 7BQ, U.K. Non-registered users may also obtain copies of Supplementary Publications but should first apply for price quotations. These are available from the Loans Office at the above address. In all correspondence with the B.L.L.D. or the Society authors must cite the supplementary publication number. International Collaboration A similar scheme (known as the National Auxiliary Publications Service) is being operated in the U.S.A. by the American Society for Information Science. Similar schemes are also being contemplated in other countries. The provision of reciprocal arrangements for the exchange of supplementary data between the various national deposition centres is being investigated.

ISSN:0300-9238    

DOI:10.1039/F298076BA001

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

J.C.S. Faraday 11, 1980, 76, 14-25 Polarizable Acid-Water Hydrogen Bonds with Aqueous Solutions of Carboxylic Acids BY MARTINLEUCHSAND GEORGZUNDEL" Physikalisch-Chemisches Institut der Universitat Munchen, Theresienstr. 41, D-8000 Miinchen 2, West Germany Received 8th December, 1978 Trifluoroacetic, difluoroacetic and formic acids have been studied, pure and in aqueous solutions, by i.r. spectroscopy. The formation of monomers from the dimers and dissociation of the acids with increasing dilution is demonstrated by bands in the spectra ;the polarizability of hydrogen bonds formed is indicated by regions of continuous absorption. At very high concentrations (n = number of water molecules per acid molecule < l), acid-water hydrogen bonds are formed. With tri- fluoroacetic acid a double minimum energy surface (with a deeper well at the anion) is present in these hydrogen bonds.They cause an i.r. continuum extending from 3OOOcm-1 over the whole range studied (3000-600 cm-l) indicating that these hydrogen bonds are easily polarizable. With difluoroacetic acid, the degree of asymmetry of these bonds is larger, but they are still polarizable, as indicated by a continuum in the range 3000-1750cm-1. With formic acid, these acid-water hydrogen bonds are largely asymmetric. In the case of trifluoro- and difluoroacetic acids, with addition of more water the absorbance of the continuum continues to increase between n = 1 and n = 3, since the degree of asymmetry of the acid-water hydrogen bonds decreases because of the influence of these water molecules.An additional reason for this intensity increase may be the coupling of transitions in the polarizable hydrogen bonds with vibrations in the environment. On further dilution, the absorbance of the continuum decreases. With increasing dilution, trifluoro- acetic acid protons transfer into water-water hydrogen bonds, i.e., H50:is formed. Also in rela- tively diluted solutions the continuum is caused not only by the easily polarizable hydrogen bonds in H50igroupings, but also by polarizable acid-water hydrogen bonds which are still present. Hydrogen bonds with double minimum energy surface or with an energy surface having a broad flat well are easily p~larizable.l-~ These polarizable bonds are indicated by continuous absorptions in the infrared spectra.4* Easily polarizable are hydrogen bonds of type B+W .B +B . H+B, i.e., bonds with which the acceptor and the donor are the same. An example of this type of polarizable bond is the hydrogen bond in the H50i grouping which occurs in dilute aqueous solutions of strong acids. A large number of bonds of this type are listed in ref. (4), table 1. It was recently shown that not only hydrogen bonds with symmetrical structure may be easily polarizable, but also bonds of type BIH B2 +B; H+B2 where B1 # B/-1° The easily polarizable hydrogen bond in the H50; grouping creates absorption continua, which begin at the OH stretching vibration band of the water molecules and extend toward smaller wavenumbers over the whole i.r.region.4* In contrast, the continuous absorbance with BIH B2 +B; --.H+B2 hydrogen bonds extends less toward smaller wavenumbers as the degree of asymmetry of the double minimum energy surface in these hydrogen bonds becomes la~ger.~-ll As the hydrogen bonds become more asymmetric, continua are only observed in the region 3200-1700cm-l and with still futher increasing asymmetry these continua change to the usual band structures observed with asymmetric single minimum energy surfaces. These changes in the i.r. spectra can easily be studied with acid-water hydrogen 14 M. LEUCHS AND G. ZUNDEL bonds. In the case of acids with pK, < 1, easily polarizable acid-water hydrogen bonds AH -OH2 +A--H+OH2axe observed when these acids can be studied at very high concentrations (water :acid ratio n < 1).With perchloric acid, the deeper well in the double minimum energy surface in these hydrogen bonds is present at the water molecules, whereas with nitric acid it is present at the mion.12*l3 With acids having pK, > 0, the polarizable acid-water hydrogen bonds should become more and more asymmetric and the polarizability should decrease with decreasing strength of the acid. This will be demonstrated for carboxylic acids in this paper. EXPERIMENTAL MATERIALS AND METHODS Analytical grade trifluoroacetic acid and formic acid were purchased from Merck, Darmstadt, W. Germany ; synthesis grade difluoroacetic acid was obtained from Fluka, Buchs, Switzerland. The spectra were recorded at 293+ 1 K with a Perkin-Elmer double-beam spectro- photometer, model 325.The air in the spectrophotometer was dried and made C02-free by treatment with silica-gel and soda asbestos. The cells used had silicon windows and a wedge-shaped layer with a mean thickness of 9.5pm. The wedge-shaped layer is necessary to avoid an interference pattern super- imposed on the spectra. The absorbance had to be corrected, since with the wedge-shaped layer the Beer- Lambert law is no longer valid. The true absorbance was obtained as described in ref. (6). The continuous absorption was determined as described in ref. (14), taking into account the background absorbance of water. The absorbance of the continuum is referred to the same background absorbance at 4700 cm-l.The degree of dissociation was determined by comparing the intensity of the vsCO; vibration of salt solutions of known concentration with the intensity of this band in the acid solutions. RESULTS AND DISCUSSION Aqueous solutions of trifluoroacetic, difluoroacetic and formic acids were studied by i.r. spectroscopy. Spectra of these liquid acids were obtained over the whole concentration range from the pure acid to dilute solutions. The pK, values of these acids are as follows: CF,COOH, various values are given in the literature, all are near 0 (0.23,150.5,160.22,l' -0.8,l -0.26,l -0.04 'O). CF2HCOOH, 1.34 (1.34,16 1.32 17). HCOOH, 3.75.15*21 1.r. spectra of aqueous solutions of these acids and their dependence on con- centration are shown in fig.1. The bands of the carboxylic acid groups and of the carboxylate anions give information about the formation of the monomers from the dimers and especially about the dissociation of these acids. With difluoroacetic acid the dissociation is estimated by a band of the salt solution at 1320 cm-l. The bands of the carboxylic groups are summarized in table 1. The assignment of the bands is obtained by comparison of the spectra of the M and D samples shown in fig. 2. The vibrational character of the component of the band pair of the coupled vibrations vc-o and dOHis determined following the criteria given by Hadii and Sheppard 22 and using literature 23 With this assignment the intense band arising at 1290 cm-l with deuteration of difluoroacetic acid remains unexplained.Especially remarkable is the fact that with the band pair caused by the coupled vibrations vc-o and SOH,in contrast to formic acid with the fluoroacetic acids, the higher wavenumber component has more vc-o and the lower more SOHcharacter. POLARIZABLE ACID-WATER HYDROGEN BONDS 0.0 0.2 (a) 0.4 0.7 Q) 1.0 O04ooo 3so03000 2500 2000 1800 1600 1400 1200 1000 aoo 600 wavenumber/cm-l wavenumber Icm-l M. LEUCHS AND G. ZUNDEL wavenumber/cm-l FIG. 1.-1.r. spectra (layer thickness 9.5 pm, 293 K) of aqueous solutions of: (a) CF3COOH (-) 13.0 rnol dm-3 (n = 0.0) ; (--.) 12.1 rnol dm-3 (n = 0.42); (----) 11.2rnol drr3 (n = 0.88) ; (---) 9.3 rnol dm-3 (n = 2.0) ; (b) CF3COOH (-) 6.3 rnol dm-3 (n = 5.1) ; (-.-.) 1.8 mol dm-3 (n = 28) ; (----) 0.6 rnol dm-3 (n = 87) ; (---) H2O ; (c) CFZHCOOH (-) 15.6 rnol dm-3 (n = 0.0); (----) 14.2rnol dm-3 (n = 0.43) ; (---) 11.2rnol dm-3 (n = 1.5) ; (d)CF,HCOOH (-) 9.3 rnol dm-3 (n = 2.6) ; (--.) 2.4 rnol dm-3 (n = 19.2);(---) H20; (e) HCOOH (-) 26.4 mol dm-3 (n = 0.0) ; (--a) 24.6 rnol dm-3 (n = 0.15) ; (---) 18.9 rnol dm-3 (n = 0.86); cf) HCOOH (-) 15.4 rnol dm-3 (n = 1.6) ; (--0) 4.0rnol dm-3 (n= 11.9) ; (---1H2O. TABLEASSIGNMENT OF BANDS OF THE ACID MOLECULES AND ANIONS coupled VOH or preferentially preferentially deuterated sample VOD VC-0 character OH character VC--0 ~OD CF$OOH 3180 1780 1760 1680 1438 1463 1450 masked 1332 ----and anion CF3COOD 2360 1780 1772 1672 1438 ----1428 1416 1030 1052 and anion CFzHCOOH 3170 1760 1752 masked 1444* 1455 1458 1238 1262 ----and anion CFzHCOOD 2340 1758 1754 1640* ----1428 1428 1036 masked and anion HCOOH 3150 1717 1715 1585* 1352* 1200 1200 1363 masked ----and anion HCOOD ----1237 1042 and anion * These vaIues are taken from the sodium salt solutions.POLARIZABLE ACID-WATER HYDROGEN BONDS 1400 1200 1009 1400 12001000 1400 1200 1000 1400 9200 1000 1400 1200 1000M wavenumber1cm-l FIG.2.-Comparison of the acid spectra with spectra of the deuterated acid in the range of the SHO and VC-OH bands. (a) CF3COOH: (-) n = 0.0; (--) n = 0.88 ; (b)CF,HCOOH : (-) n = 0.0; (--) n = 0.82; (c) HCOOH: (-) n = 0.0; (--) n = 0.86; (d) FBCOOD: (-) n = 0.0; (--) n = 0.98; (e) F,HCOOD: (-) n = 0.36; (--) n = 1.28; (f)HCOOD : (-) n = 4.77.DEGREE OF DISSOCIATION TRIPLUOROACETIC ACID [fig. l(a) and (b)]. The removal of protons from the anion is indicated by v, at 1438 cm-l [fig. l(b)]. From this band, the degree of dissociation is determined and plotted in fig. 3 as a function of the molarity MHloand as a function of n, the number of water molecules per acid molecule. For comparison values determined by Raman spectroscopy by Covington et aZ.17are also shown. The i.r. and Raman data both show, with good agreement, that the protons are removed from the anions with increasing n. The degree of dissociation can also be determined from the vc=o band of the non-dissociated acid molecules at 1760 cm-l.A weak shoulder in this position, which is still observed in the spectrum of the 1.8 mol dm-3 (n = 28.0) solution, demonstrates that, even in this relatively dilute solution, non-dissociated molecules are still present. With these spectroscopically determined degrees of dissociation, however, one must always keep in mind that the acid molecules observed as dissociated axe not only those in which the protons are removed from the anion and present in H50;, but also those in which the protons are present in proton limiting structure PI in the acid-water hydrogen bond (see following section). DIFLUOROACETIC ACID [fig. d(c) and (41. In the spectrum of the 2.44moldm-3 M. LEUCHS AND G.ZUNDEL (n = 19.2) solution, v, is masked; therefore the band at 1320 cm-l, which is also observed with the sodium salt, is used to determine the removal of protons from the anions. This band is already noticeable in the spectrum of the 9.3 rn~ldrn-~ solution as very weak shoulder. A quantitative estimation shows, however, that in the 1 mol dm-3 solution the degree of dissociation is < 0.15. n a 10 543 2 I I Ill I' Mlmol dm-3 FIG.3.-Degree of dissociation of trifluoroacetic acid. (+,Results of Covington et a2.l') FORMIC ACID [fig. l(e) and 01. From studies with salts of formic acid it is known that v,, of the carboxylate anion is found at 1585 cm-1 and v, at 1352 cm-l. Also with the most dilute solution of formic acid no bands in these positions are observed.Thus, under these conditions, the number of dissociated formic acid molecules is too small to be observed in the spectra. NUMBER OF WATER MOLECULES PER ACID MOLECULE <1 FORMATION OF THE ACID MONOMERS TRIFLUOROACETIC ACID [fig. l(a)]. With addition of water, vOH of the dimers at 3180 cm-l vanishes. vcpo shifts from 1780 to 1760 cm-l and is strongly broadened. A aOHvibration arises at 1332 cm-l and a yoH vibration at 980 cm-l and the vc-o band at 1463 cm-l is strongly broadened. DIFLUOROACETICACID [fig. l(c)]. With addition of water molecules vOH,the stretching vibration of dimers at 3170 cm-', vanishes. ve0 shifts from 1760 to 1752 cm-l and the aOHvibration shifts from 1238 to 1262 cm-l. ACETIC ACID [fig. l(e)].With addition of water, vOH of the dimers at 3150cm-l vanishes. The band with aOHcharacter at 1363cm-l shifts toward larger wave- numbers and becomes masked. All these results show that the caxboxylic acid dimers dissociate to monomers because of the addition of water molecules. ACID-WATER HYDROGEN BONDS TRIFLUOROACETIC ACID [fig. l(a)]. With addition of water continuous absorbance is observed. This continuum begins at the OH stretching vibration bands of the water molecules and extends toward smaller wave numbers over the whole region. In fig. 4(a), this continuum is plotted as a fmction of n, the number of water molecules POLARIZABLE ACID-WATER HYDROGEN BONDS per acid molecule, and as a function of the molarity of water. The continuum demonstrates that the acid-water hydrogen bonds formed, COH -OH2 + CO-* H+OHz, I I1 are easily polarizable proton-transfer hydrogen bonds.A double minimum energy surface is present in these hydrogen bonds. The dissociation behaviour of this acid, discussed in the preceding section, shows, however, that at y1 = 1, the weight of proton limiting structure I is much greater than that of structure 11. Thus, at n = 1, the deeper well of the double minimum is at the anion. The residence time of the proton in the deeper well is sufficiently long that the SOHband is observed at 1332 cm-l c 0.0 1 0 10 MH,o/mol dm-3 (c) n -0 . 0 0 0 10 MH,o/mol dm-3 FIG.4.-Continuum as a function of the molarity of water and the mol ratio of water to acid, n.The background absorbance remaining at n = 0 is caused by slopes of bands. (a) CF,COOH; (b)CFZHCOOH ; (c) HCOOH. M. LEUCHS AND G. ZUNDEL and the yOH band as a very broad band with a maximum at rn 980 cm-l. The result that the continuum extends toward smaller wavenumbers shows, however, that the double minimum energy surface is not very asymmetric. The water molecules in these acid-water groupings cause a stretching vibration at 3520 cm-1 and a scissor vibration at 1620 cm-I. The positions of these bands demonstrate that the OM groups of the water molecules in the acid-water groupings are bound to their environment only by very weak hydrogen bonds. The acceptors of these bonds are preferentially 0 atoms of -COOH groups, which are only very weak hydrogen bond acceptor sites.DIFLUOROACETIC ACID [fig. 1(c)]. With addition of water, a continuous absorbance arises in the region 3000-1700 cm-l. This continuum is, however, less intense than that with trifluoroacetic acid [cf. fig. 4(a) and (b)]. Furthermore, below 1700 cm-l the increase in the background absorbance may be explained by the slopes of the bands, for instance at = 1000 cm-l by the yOH vibration and below 800 cm-1 by the torsional vibration of water molecules. In fig. 4(b) the increase in the absorbance of the continuum at 1900cm-l is plotted as a function of n and of the molarity of water. This continuum is caused by acid-water hydrogen bonds. COH * OH2 +CO-H+OH2 I I1 The continuum shows that these bonds are still polarizable.At n = 1, however, proton limiting structure I1 has no noticeable weight, since, as discussed in the preceed- ing section, no bands of dissociated groups are observed. The deeper well of the double minimum energy surface is at the anion. This energy surface is largely asymmetric. From theory it is known 24 that with an increasing degree of asymmetry of the double minimum energy surfaces, the residence time in the higher well decreases much more markedly than the fluctuation frequency of the proton. Even when the residence time of the proton in the higher well is very short, the polarizability is smaller but still appreciable. This theoretical result was confirmed by results with caxboxylic acid +N-base systems.It was shown in these studies [see fig. 2 in ref. (6)] that even if the proton is largely located at the N-base, the absorbance of the con- tinuum is weaker, but can still be observed. As observed with difluoroacetic acid, however, these continua no longer extend to the low wavenumber region. The continuum shows a band-like structure, for instance, a broad maximum at z 1950 cm-l. Such band-like structures of continua with acid-water hydrogen bonds are discussed in detail in ref. (25). The sharp bands which are superimposed on the continuum in the region 3000-2500 cm-l are caused by combination vibra- tions and overtones intensified by Fermi resonance, as discussed by Wolff and 26 All these results and considerations taken together demonstrate that with difluoroacetic acid the energy surfaces in the acid-water hydrogen bonds are relatively asymmetrical, but not so asymmetrical that they cause sharp bands instead of the continuum.Thus, the polarizability of these bonds is much smaller than that of symmetrical hydrogen bonds with double minimum, but much larger than the polarizability of asymmetrical hydrogen bonds. The water molecule in the acid-water groupings formed by difluoroacetic acid causes two OH stretching vibrations, at 3630 and 3500 cm-l. The band at 3630 cm-l shows that the number of non-hydrogen-bonded OH groups is relatively large and the band at 3500 cm-1 indicates that the other OH groups of these water molecules POLARIZABLE ACID-WATER HYDROGEN BONDS are bound only via relatively weak hydrogen bonds to acceptor sites of 0atoms of the -COOH SOUPS.FORMICACID [fig.l(e)]. When the broad band of the OH stretching vibration in the formic acid dimers vanishes, a broad absorption in the region below 3250cm-l arises, which extends to 1800 cm-l, but is much less intense than with difluoroacetic acid. This absorbance is plotted in fig. 4(c) as a function of n and of the water molmity, MHz0. This absorbance is caused by the acid-water hydrogen bonds. With regard to the intensity distribution of this absorbance, these acid-water hydrogen bonds are largely asymmetrical, and the polarizability of these bonds is much smaller than with difluoroacetic acid. Similarly, as with difluoroacetic acid, the bands which are observed in the region 3000-2500cm-l are caused by overtones and combination vibrations which are intensified by Fermi resonance with the funda- mental transition in the acid-water hydrogen bond-as discussed by Wolff and coworker^.^ 26 NUMBER OF WATER MOLECULES PER ACID MOLECULE >I TRIFLUOROACETIC ACID.Fig. 5(a) shows that the absorbance of the continuum still increases when the second and the third water molecules per acid molecule are added. Thus, the absorbance per polarizable acid-water hydrogen bond increases because of the addition of water molecules. This is explained as follows : fig. 3 shows that a increases considerably with the addition of these water molecules. As is well 0 1 2 3 4 5 n FIG.5.40ntinuous absorption as a function of n.(a) CF3COOH; (b)CF,HCOOH. M. LEUCHS AND G. ZUNDEL known from other systems,6* *-lo*l2$ l3 the addition of water molecules increases the weight of the polar proton limiting structure (structure 11). Hence, the degree of asymmetry of the acid-water bonds decreases and the polarizability and the absorb- ance of the continuum increase. The absorbance increases, since more and more intense transitions occur in the wavenumber range 2500-1000 cm-l, when the degreeof asymmetry of the polarizable hydrogen bonds decreases. An additional increase of the absorbance may occur, since transitions in the polarizable hydrogen bond couple with vibrations in the environment, due to the large polarizability of the acid-water hydrogen bonds. Hence the absorbance of the continuum increases from n = 1 to n = 3, because of the decreasing asymmetry of the hydrogen bonds.After the maximum at n = 3, the absorbance of the continuum decreases as a result of decreasing concentration of the polarizable acid-water hydrogen bonds due to dilution. t t Ol0 '0 Illllllllll0.oL 1 0.0 5.O 10.0 M/mol d~n-~ FIG. 6.-Continuum as a fwction of the molarity M/mol dm-3 of the acid : (-) continuous absorption of CF3COOH,(---) continuous absorption of a HCl solutionwith the same concentra- tion of protons as that of dissociated CF,COOH molecules. With increasing dilution, protons from the polarizable acid-water hydrogen bonds transfer into the network of hydrogen-bonded water molecules, i.e., H50; is formed.The easily polarizable hydrogen bond in this grouping now contributes also to the continuous absorbance. In relatively dilute solutions of trifluoroacetic acid, besides H,Oz, acid-water hydrogen bonds are still present and contribute to the continuum. This is demonstrated by the following consideration : in fig. 6 the absorbance of the continuum is plotted as a function of the acid concentration. The dashed curve shows the absorbance of the continuum which would be expected if all protons removed from the anion were present in H5O; groupings. This curve is calculated from the degree of dissociation (fig. 3) and from data obtained with aqueous HC1 solutions. Fig. 6 shows that with CF,COOH concentrations > 1.5 mol dm-3, the absorbance of the continuum is stronger than it would be if all protons which are removed from the anion were present in H50; groupings.Thus, also down to these concentrations, polarizable acid-water hydrogen bonds are present and contribute to the continuum. This result is confirmed by the fact that even in the spectrum of the 1.8 mol dm--3 solution [see fig. l(b)] a weak shoulder is observed at 1760 cm-l, POLARIZABLE ACID-WATER HYDROGEN BONDS indicating the presence of proton limiting structure I of polarizable acid-water hydrogen bonds. DIFLU~ROACETICACID. Fig. 5(b)also shows that with this acid, the absorbance of the continuum increases when a second and a third water molecule are added. As with trifluoroacetic acid, this is caused by decreasing asymmetry of the polarizable acid- water hydrogen bonds.This is confirmed by the result that in the spectrum of the 9.3 mol dm-3 solution (n = 2.6), a weak shoulder at 1320 cm-l [fig. 1(4]is observed, indicating a noticeable weight of proton limiting structure I1 of the acid-water hydrogen bond. CONCLUSIONS With the carboxylic acids studied, the addition of water (n = 0 to n = 1)causes the formation of acid-water hydrogen bonds. In the case of trifluoroacetic acid, these hydrogen bonds are easily polarizable. AH OH2 +A-H+OH2 I I1 At n = 1, the weight of proton limiting structure I is larger than that of structure If. The deeper well of the double minimum energy surface is present at the anion. This bond causes an i.r.continuum, which extends from 3200 cm-l toward smaller wavenumbers over the whole i.r. range. With difluoroacetic acid, the well of the double minimum energy surface at the anion is deeper and hence the energy surface much more asymmetrical. The hydrogen bonds are still polarizable, but the con- tinuum extends only over the range 3200-1750cm-l and shows a band-like structure. In the case of formic acid, the acid-water hydrogen bonds are largely asymmetrical. Thus in the series of acids from formic to trifluoroacetic the energy surface in the acid-water hydrogen bonds becomes increasingly symmetrical and their polarizability increases. With trifluoro- and difluoro-acetic acids, the addition of a second and third water molecule per acid molecule increases the weight of proton limiting structure 11.The degree of asymmetry of the double minimum energy surface decreases and the polarizability of these hydrogen bonds increases, because of the addition of water molecules. In relatively dilute solutions (1.5 mol dm-3) of trifluoroacetic acid, besides the easily polarizable acid-water hydrogen bonds the easily polarizable hydrogen bond in HSOh also contributes to the continuum. We thank the Deutsche Forschungsgemeinschaft and the Fonds der Deutschen Chemie for providing the facilities for this work. E. G. Weidemann and G. Zundel, 2.Naturforsch., 1970,25a, 627. R. Janoschek, E. G. Weidemann, H. Pfeiffer and G. Zundel, J. Amer. Chem. Soc., 1972, 94, 2387. R. Janoschek, E.G. Weidemann and G. Zundel, J.C.S. Faraday 11, 1973,69,505. G. Zundel, in The Hydrogen Bond-Recent Developments in Theory and Experiments, ed. P. Schuster, G. Zundel and C. Sandorfy (North Holland, Amsterdam, 1976), vol. 11. G. Zundel, Hydration and Intermolecular Interaction (Academic Press, N.Y., 1969 and Miry Moscow, 1972). R. Lindemann and G. Zundel, J.C.S. Furaday 11, 1977,73,787.'M. Matthies and G. Zundel, Biochem. Biophys. Res. Cumm., 1977,74,831. A. Nagyrevi and G. Zundel, J. Phys. Chem., 1978,82,685. R. Lindemann and G. Zundel, Biopolymers, 1977, 16,2407. M. LEUCHS AND G. ZUNDEL lo R. Lindemann and G. Zundel, Biopolyrneus, 1978,17,1285. l1 B. Brzezinski and G. Zundel, J.C.S. Faraday II, 1976,72,2127. l2 M. Leuchs and G.Zundel, J.C.S. Faraday 11, 1978,74,2256. l3 M. Leuchs and G. Zundel, J.Phys. Chem., 1978,82,1632. l4 D. Schioberg and G. Zundel, Canad.J. Chem., 1976,54,2193. l5 A. Albert and E. P. Serjeant,Ionization Constants of Acids and Bases (Wiley, New York,1962). l6 J. L. Kurz and J. M. Farrar, J. Amer. Chem. SOC.,1969,91,6057. l7 J. W. Lason and L. G. Hepler, in Solute-Solvent Interactions, ed. Cotzee and Ritchie (Marcel Dekker, New York, 1969).A. K. Covington, J. G. Freeman and T. H. Lilley, J. Phys. Chem., 1970,74,3773. l9 G. C. Hood, 0.Redlich and C.A. Reilly, J. Phys. Chem., 1955,23,2229. 2o E. Grunwald and J. F. Haley, J.Phys. Chem., 1968,72,1944. 21 H. S. Harned and N. D. Embree, J. Amer. Chem. Sac., 1934,56,1042. 22 D. Hadii and N. Sheppard, Proc. Roy. SOC.A, 1953,216,247. 23 H. Wolff, H. Miiller and E. Wolff, J. Chem. Phys., 1976,64,2192. 24 E. G. Weidernann and G. Zundel, 2.Naturforsch., 1973,28a, 236. 25 M. Leuchs and G. Zundel, Canad.J. Chem., 1979,57,487. 26 H. Wolff, B. Nikolaus and E. Wolff, J. Chem. Phys., 1976,65,3394. (PAPER 812114)

ISSN:0300-9238    

DOI:10.1039/F29807600014

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

J.C.S. Faraday II, 1980,76,26-41 Vibrational Spectra of Matrix Isolated AlzC16 Isotopic Fine Structure and Valence Force Field BY MICHEL TRANQTJILLE" AND MONIQUE FOUASSIER Laburatoire de Spectroscopie Inf'rarouge associ6 au C.N.R.S., UniversitC de Bordeaux 1, 351 Cours de la Libbration, 33405 Talence, France Received 28th December, 1978 High resolution i.r. and Raman spectra have been recorded for the bridged dimeric aluminium chloride molecules isolated in argon and nitrogen matrices at very low temperatures. An accurate valence force field has been calculated from the frequencies of fifteen fundamental modes and some isotopic shifts due to the 35CI,37Cldistribution. The calculated isotopic frequencies and the isotopic patterns are shown to be in agreement with the experimental results.From thermodynamic and spectroscopic considerations, the unobserved ring-puckering mode is predicted to occur at very low frequencies (iN 10 cm-I). The Al-CI bond dissociation energies are 270 and 170 kJ mol-1 for terminal and bridging atoms, respectively; the force constants of the same bonds are 226 and 130 N m-l. Recently there has been considerable interest in the study of i.r. and Raman spectra of monomeric aluminium chloride in order to clarify the conclusions of spectroscopists.1-4 Overlapping of the spectral components of monomeric and dimeric molecules at very high frequencies has made this region the subject of detailed discu~sion.~-~ It is therefore of interest to obtain an exact spectrum of the dimer in order to calculate a reliable force field and to explain the complex absorption patterns obtained at high resolution with natural abundance of chlorine isotopes.Although several authors have recorded the vibrational spectrum of A12C16, the 17 active fundamental frequencies have not been observed. The structural para- meters of the dimer have been determined in the gas phase s' and in the liquid phase.* The conclusions agree closely with a molecular structure consisting of two tetrahedral A1Cl4 units sharing a common edge. The non-planar bridged model has the point group D2,, and the 18 fundamental vibrations of A12C16 belong to eight species as follows : The Rman (9)and i.r. (u) wavenumbers are mutually exclusive in their activity.The A,, frequency is forbidden both in the i.r. and Raman spectra and the four A, are expected to be polarized in the Raman spectrum. The numbering of the vibrational modes is taken from ref. (9). The first Raman spectrum of liquid A12C16 lo permitted the identification of three A, lines at 506, 340 and 217cm-l since they are polarized. The fourth is found in the intense and broad line at 100 cm-l.ll In the gas phase, Beattie and Horder l2 have observed two components at 117 and 99 cm-l ; the lower component is polarized. Torsi et aL1 draw a sirnilax conclusion for the liquid phase. Recently, Beattie et aL2 have recorded the Raman spectrum in an argon matrix under medium resolution. The first i.r. spectrum from Klemperer,14 in emission spectroscopy, shaws the 26 M.TRANQUILLE AND M. FOUASSIER three highest frequencies. All the remaining studies were of absorption by the matrix isolated ~pecies.l-~* Only recently, Perov et all5 studied the far4.r.l5 spectrum where they found a 378cm-l band not previously reported. Several force fields have been calculated based on incomplete data ;9s 11* 14* 16-1 manyassignments remain doubtful.'* l6, l7 This work was undertaken in order to obtain further detail on the bending mode frequencies and assignments. This knowledge would permit calculation of an accurate force field from the isotopic frequencies. With this in mind,we have recorded first the trapped gas spectra at 20 K and, secondly, the matrix i.r. and Raman spectra which contain, under high resolution, detailed information on the isotopic molecule frequencies.Furthermore, the isotopic pattern analysis leads us to an unambiguous assignment of the stretching modes. This is the first work in which both Raman and i.r. spectra are analysed in the range 700-20 cm-l (albeit on different samples). A general valence force field calculation is presented based upon isotopic data. The bond force constants obtained are compared with those of the monomer A1Cl3 and the bond dissociation energies are deduced. The calculated wavenumbers and the available thermodynamic data make it possible to estimate the frequency of the vl0 ring-puckering mode. Finally, the shapes and the complexity of the patterns in the matrix experiments resulting from both isotopic and "environment effects " splitting are discussed.EXPERIMENTAL The matrix isolation i.r. and Raman studies were carried out using a Cryophysicscooling unit (Cryodine 21) which was incorporated in a conventional high vacuum system operating down to T0rr.19 The same vacuum shroud was used for mid-i.r., far4.r. and Raman spectroscopy. The samples of aluminium chloride were obtained from Fluka (puriss grade) and were used with or without sublimation. We obtained similar results in both cases. The oven was filled in a dry box and introduced into the shroud under a stream of anhydrous nitrogen or argon. A Pyrex oven l9 was used to sublimate the aluminium chloride sample. On leaving this oven, the vapour was mixed with a large excess of argon or nitrogen (high purity N50 Air Liquide) and deposited on the cooled surface (18 K) after traversing a path M 40mm.The oven temperature was monitored by a chromel-alumel thermocouple at 330K. Matrix gas flows were typically M 1-2 mmol h-I. The vacuum in the shroud was 5 x Torr during deposition. The matrix ratios of these experiments were not measured. Depositiontimes of 6 h were commonly used. Dilution by a factor of 2 does not affect the i.r. spectra. The Raman nitrogen matrix is more concentrated than the others. The mid-i.r. spectra were recorded on a Perkin-Elmer 180 spectrophotometer calibrated in frequency and resolution with water vapour lines.2o The far4.r. spectra were obtained on a Polytec FIR 30 Fourier transform apparatus.The matrix was deposited onto a cooled CsI window for examination down to 150cm-I. Between 400and 20 cm-' we used a polished silicon window as a deposition surface with two thin polyethylene windows (1 mm)on the vacuum shroud. The temperature of the samples was controlled using a chromel-gold (0.07% Fe) thermocouple embedded into a copper block attached to the window. The frequencies are determined within & 1 m-l. For Raman spectroscopy, the matrix was deposited onto a polished oxygen-free high conductivity copper tail. The incidence angle of the laser beam was M 60". We have used a Coderg T800 instrument with a Spectra Physics argon ion laser excitation (model 165, 5145 or 4880 A). The spectrometer is calibrated using a neon lamp, the Raman shifts are measured within fl cm-l.When Nzmatrix material is used, the temperature of the matrix itself at the focus point of the laser can be measured accurately using the I(Stokes) VIBRATIONAL SPECTRA OF MATRIX ISOLATED ~1~~1~ /I(anti-Stokes) ratio for the v = 31 cm-l line which corresponds to a phonon band of the nitrogen crystal. The power levels were typically 300-6OOmW at the sample. For a nitrogen matrix, we measured a 3 K rise in temperature at the sample using 1 W laser power. RESULTS AND DISCUSSION Our spectra are reported in fig. 1. The mutual exclusion between i.r. aad Raman indicates a centrosymmetric entity as expected for the dimer molecule (table 4). This work leads us to locate 8 Raman and 7 i.r.fundamental frequencies. The present Raman spectrum of Al,C16 matrix isolated in argon is similar to the Beattie et aL2 spectrum except for the 77cm-l line which we have rejected. This feature stems from an argon plasma emission. It is possible to eliminate such an v/cm-l 700 500 300 100 1 I I I I I 500 300 100 F1crn-l FIG.1.-Infrared and Raman spectra of A12C16 between 700 and 20 cm-'. (---) spectra at 20 K after annealing to 120K. Darkened bands are due to matrix material and/or slight amount of water in the Ar spectrum. M. TRANQUILLE AND M. FOUASSIER effect by adding a premonochromator before the sample or by changing the excitation line. The weak 438 cm-l line observed in gas and liquid phase spectra is not seen in any matrix experiments ; it has been discussed in detail by Miller.16 We agree that it is due to a v3 mode overtone because its counterpart appears in the A12Br6 and A& spectra.Some doubt exists for the v6 stretching mode (Big) frequency between the two observed values at 318 and 285 cm-l ; we will discuss this assignment after we have presented the results of the calculation. In the stretching region, all i.r. spectra show four bands as expected. The lowest wavenumber (320 em-l) has been attributed to an impurity ;I interpretation of its absorption profile shows that it arises from a fundamental mode. The relative intensities of the 620 and 480 cm-l bands found by Beattie et aL2are different from those observed by the other investigators ; this behaviour may be caused by different resolution of the spectrometers since the sharpness of the bands depends on the deposition rate and matrix ratio.Only Perov et all5 have observed a 378 cm-l i.r. band; it is probably an artifact created near the upper limit of their spectrometer range. More surprising, these authors do not detect the usual 320 cm-l band. TRAPPED GAS SPECTRA In the far-i.r. region we have observed a band at 134 cm-l, not previously reported, which is due to a bending mode. These spectra are of great importance because they allow the detection of eventual aggregate formation in the matrix spectra. After annealing to 120 K (fig. l), these spectra become quite different being determined by the ionic structure of solid aluminium chloride.21 The Raman spectrum is then dominated by the 307 cm-l line; this result agrees with ref.(22). The ir. spectrum of an annealed sample shows 13 absorptions at : 121w, 146m, 180111, 296m, 320s, 343w, 398s, 417w, 441m, 453w, 476m, 507s and 602vs; eight of these wavenumbers (cm-l) differ from those observed after direct deposition and the strong bands at 507 and 602 cm-l correspond to very weak features in the A12C16 spectrum. MATRIX SPECTRA When single crystals are not available, as for the spectroscopy of supercooled gases, low temperature matrix isolation is presently the best means for a detailed analysis of the pure vibrational spectrum. In this case, the trapped gas and matrix spectra are similar except for the sharpness of the bands in the latter case.In the far-ix. region, the spectra show a well resolved doublet at 143-135 cm-l stemming from two bending modes. We have not observed the vl0 ring-puckering mode expected below 1OOcm-l. v5 is i.r. forbidden, but we have observed the three remaining active vibrations. In the corresponding Raman region one line is missing; we assume it is the BSgmode expected with a low intensity because no stretching vibration exists in this symmetry species. Under high resolution, we have obtained detailed isotopic patterns on i.r. stretching vibrations and for the most intense Raman line (fig.2). Unfortunately, the isotopic splittings cannot be observed below 25Ocm-l for the bending modes. The two higher frequency i.r. bands are detailed in fig. 3.In an argon matrix, the spectra exhibit features which are less well-spaced than in nitrogen; they axe considered to result from multiple isotopic patterns caused by "environment effects ". For N2matrices, we observe three different patterns ; the central part disappears after annealing (fig. 3). The two remaining patterns are separated by 6 cm-l, indicating that mole- cules strongly interact with the matrix. However, the annealing process has no appreciable effect on the argon matrix. VIBRATIONAL SPECTRA OF MATRIX ISOLATED A12Cl, 615 610 425 420 325 * 320 i1cm-l FIG.2.-High resolution i.r. spectrum of A12C16 in Nzmatrix. Isotopic patterns due to chlorine and Y17. (a) Calculated spectra from Maroni's force field.isotopes h natural abundancy for V8, ~13 (b) Calculated spectra from our non-refined set 2. (c) Calculated spectra from our refined force field. (d) Observed spectra. The resolutions are 0.4cm-I for the 615 cm-I bands, 0.6 cm-l for the 425 cm-' bands and 0.95 cm-I for the 320 cm-1 bands. (4 A 'I 0.5 (c) 41-0.3cm" 0.5 I 82 o* 0 620 615 610 620 615 610 605 lJIcm-1 vlcm-I FIG.3.-High resolution i.r. spectrum of AlzC16 in Ar [(a)and (b)]and N2 [(c) and (dl1 matrices at 20 K in the VS [(a) and (c)] and v16 [(b) and (d)]regions. (---) Spectra at 20 K after annealing to 35 K. The argon spectra are identical before and after annealing. M. TRANQUILLE AND M. FOUASSIER Two comments concerning these spectra can be made : (i) for each matrix, regaxd- ing vs and v16, we observe an alternation of the intensities as a function of wave- numbers, while for a given mode the relative intensities are changed between the argon and nitrogen ;(ii) on annealing the N2matrix, one type of" metastable environ- ment " is destroyed ; then, despite the above remark, the intensities of the highest wavenumbers axe enhanced for both the vs and v16 modes. Fig.3 shows that the isotopic patterns can be more easily interpreted from N2 matrix spectra. The isotopic shifts are almost identical in both matrices (table 1).Among the 21 isotopic arrangements of Al,C16 for natural abundance of chlorine isotopes (fig. 4), 7 molecules constitute < 1 % of the total and they are omitted in the following discussion and calculation.70 % of the remaining molecules are represented by I, IT, I11 and VIII. TABLE1 .-OBSERVEDWAVENUMBERS (cm-l)FOR I.R. MATRIX EXPERIMENTS nitrogen matrix argon 622.1 1,1 621.0 620.25 619.5 a618.7 l.l a617.6 v8 615.8 l.l BIZ4 614.7 1.5 613.2 2.0 611.2 482.5 1.5 479.6 481.0 1.4 v16 485.0 483.6 482.6 l.4 l.o 1.5 478.5 476.4 1,5 B3U 481'1479.65 1.45 474.9 1.4 473.5 426.4 2.2 424.2 2.2 422.0 v13 B2u 422.1 420.2 418.2 1.9 2.0 322.7 v17 320.3 320.7 sh. B3u 318.8 sh. a Only before annealing. For a mode which involves only bridging A1-C1 bonds, three isotopic arrange- ments are expected and lead to a triplet structure with 11:7 :1 relative intensities (e.g.,fig. 2 the 425 cm-l band).For the other modes it is not easy to forecast the isotopic pattern. For example, vg at 615 cm-l, which involves the motion of two identical terminal A1-C12 groups, would give a triplet as described above for separ- ated vibrations of these groups ; the observed quartet suggests that the two terminal A1-C12 groups are interacting in the vs mode. VIBRATIONAL SPECTRA OF MATRIX ISOLATED AI2CIs [ number ] CD CI [ percentage ]24 l2 1 VI VII VIII clM16 4 4 XI XI1")o( .)4( 2.5 2.5 XVI xv I1 0.4 0.2 XIX 0.1 FIG.4.--;Labelled molecules of AlzCls and composition of a sample containing chlorine isotopes in natural abundance, Jc, inversion centre; 0, 37Cl. M. TRANQUILLE AND M. FOUASSIER TABLE2.-GEOMETRY AND COORDINATESOF A12a6 USEDIN THE FORCE CONSTANT CALCULATION ~~~ aluminium 1 aluminium 3 az/12 indicates the average in the sum of three internal coordinates determined by the dihedral angle variations between planes which have 1-2 as common bond.For example : 7/12 = $(A77 123 +AT8 12 3 +AT412 3). Six remaining redundancies are not described. They lead to six zero eigenvalues after diagonalization of the Gmatrix, Il-2 VIBRATIONAL SPECTRA OF MATRIX ISOLATED A12C16 To continue the interpretation, vibrational calculations were necessary. First, we calculated the 14 isotopic frequencies for each mode of the most abundant mole- cules using Maroni’s force field.ll This preliminary calculation shows, for the i.r. band at 615 crn-l, that all the frequencies are concentrated in a four-band pattern within the experimental resolution (fig.2).It permits the unambiguous determination of the isotopic shifts for use in the refinement. However, the calculated isotopic shifts are not equal to the experimental values, demonstrating that Maroni’s force field is not accurate (fig. 2). To the four most abundant molecules, I, 11, 111and VIII, we have introduced V to take into account the lowest frequencies observed for the bridging modes. The following wavenumbers (cm-l) have been used : molecule I I1 I11 V VIII VZ&) VdBlU) v 1 3(B2u) V 16(&4) 348.0 616.0 421.5 478.0 348.0 614.9 421.5 476.5 345.2 616.0 419.3 478.0 342.7 -417.1 - 345.2 614.9 419.3 476.5 For molecule I, the observed wavenumbers are those of the trapped gas spectrum, the isotopic frequencies being recalculated using the isotopic shifts of the N2matrix.FORCE CONSTANT CALCULATION A general valence force field has been calculated using the Wilson’s G.F. method.23 The computer program has been described previously ;24 for the refinement the correlated force constants are expressed as linear functions. A C.I.I. Iris 80 computer was used. In order to eliminate some doubt concerning the choice of a set of force constants our method consists of starting with the known AlCl, force field.25 This choice implies the set of group coordinates described in table 2. The structural parameters axe taken from ref. (7). Table 3 (set 1) presents the AlC1, force field for our C2,coordinates referred to Al-Cl bond lengths in A12C16.Set 2 is derived from set 1 by considering the difference between terminal and bridging stretch frequencies. The chosen values of Fv(AlC1,) and FV(Alc1b) in set 2 give a best fit between observed and calculated wavenumbers (table 4); besides they agree well with previous reported force constants.ll* 16-18 The bending force constants are perturbed, on the basis of internal coordinates, as the corresponding stretching force constants, e.g. : I;G(Cl,AlCl,) = l.lFi3(ClAlCl) in AlCl, ; E’d(C1,A1Clb) = Flj(ClAlC1) in AlCl, .* Changing set 1 to set 2, we observe a small effect on calculated bending frequencies. Fi3y and Fz are not predicted by AlC1, transfer; the latter is arbitrarily fixed to calculate the highest possible frequency of the torsional mode whilst the former value does not appreciably change the calculated frequencies except for v3.These preliminary calculations lead to a better understanding of the assignments of the bending modes. v5 is calculated to be lower than the observed frequency. v, is expected at higher wavenumber than v12 and we propose, respectively, 163 and 121cm-l. For the i.r. species, vg is the highest frequency, probably 176 cm-l ; for the other two, the calculation indicates v18 > ~14. The above assignments seem to be correct since a coherent perturbation of the primary force constants gives a good set of wavenumbers. A negative value is * A similar hypothesis gives excellent results when comparing AICI; and AIBr;; force fields in evaluating the A1C12Br; force field.M. TRANQUILLE AND M. FOUASSIER necessary for f~,(AlCl~~)-r(AlCl,) to adjust the Bzs and B1, modes, an opposite effect is required for fv,(AlCl,,) -w(A1Cl2) on the B,, and Bzu modes. The inter- group interaction force constant fv(AlC1,) -v(AlCl,) with chlorine as common atom is necessary to adjust the different bridging modes frequencies. Its high value arises TABLE3.-M2C&j FORCE CONSTANTS The stretching force constants are expressed in mdynkl, the bending force constants in mdyn A rad-2 and the stretch-bend interaction force constants in mdyn rad-l. from after Maronil set 1 set 2 refinement 2.75 2.008 2.40 2.257 1.31 2.008 1.30 1.299 0.634 0.638 0.711 0.666 1.091 0.591 0.454 0.367 0.594 0.732 0.730 0.596 0.594 (O.O)U (0,O)a 0.36 0.497 --0.179 0.495 [0.60] [0.10] 0.188 O.49Sc 0.609 0.lC 0.432 -0.20 0.179 0.163 0.065 0.0 b 0.0 0.324 0.0 b 0.0 o.oc 0.33 0.179 0.170 0.113 0.0 -0.092 -0.092 -0.087 0.0 0.092 0.059 -0.001 0.0 0.112 0.131 0.022 0.0 -0.112 -0.106 -0.120 -0.095 -0.118 -0.085 -0.042 0.0 0.205 0.164 0.329 0.0 0.205 0.225 -0.336 0.0 b 0.0 0.039 0.0 b 0.0 0.066 a The corresponding coordinates are not used in the Maroni’s calculation.ll Set 1 : AlC1, force field 25 expressed in C2,,coordinates.Set 2 : Modified set 1 by considering the energy differences between bridging and terminal bonds.Non-existing values in the AICI, system. Constrained force constants in the refinement. from the low frequency of v6 at 285 cm-l. In order to obtain a good fit, we have finally introduced for the refinement : f(r-r), f(w-w) and f(tw-tw) ; these constants act selectively on the v7 frequency; we have chosen all three because they are com-binations of the same internal coordinate force constants. We have used 29 experimental frequencies to refine 19 unconstrained force TABLE 4.-oBSERVED AND CALCULATED AfzCI6 WAVENUMBERS (Cm-' ) ij/cm-l (observed) Ar N2 trapped set 2a refined a assignment matrix matrix gas force field force field 523 520 519 473 517.8 342 347 348 345 348.0 219 221 219 233 218.4 106.5 107 107 109 104.9 284 289 285 356 285.3 166 162 163 190 162.0 612 604 605 569 604.6 121 122 121 1 69 121.5 n.0.n.0. n.0. 155 160.6 n.0. n.0. n.0. 81 77.6 621.5 622 61 6 570 616.3 174 175 176 231 175.6 n.0. n.0. n.0. 1421 [42.0]422 426.5 421.5 401 421.6 135 135.5 134 133 132.7 485 482.5 478 478 478.3 320 322 320.5 357 321.O 143.5 143.5 142.5 157 143.1 331 318 318 628w 606.6 620sh V.W. 608.5 605.7 600sh V.W. V.W. 146sh 575v.w. 519v.w. w o\ 7lcrn-l (calculated) P.E.D.& 173FV(AlClb) 11FV(Mclb), 136Fw(AlC12) 87Fv(AIClt),11Fr(AIC12) 51Fv(AlClt), 102Fr(A1Cl2) 89Ftw(AlC12) 104Ft~(AIC12) 82Fv(AlClt),13Fr(A1CI2) 54Fv(A1CIt), 84Fr(Ncl2) n.0. : not observed. [ ] The corresponding force constant is constrained in the calculation.a Wavenumbers of the A1235C16 molecule. lOOL&&/&. Terms < 10 are omitted. M. TRANQUILLE AND M. FOUASSIER constants. The results are reported in tables 3 and 4. Ftw(AlC1,) has been con- strained because we do not have any experimental data concerning the twisting modes. The resulting normal modes (table 4) show a slight mixing between stretching and bending vibrations. A considerable mixing occurs between terminal and bridged Al-Cl vibrations in the v,(A,) and v16(&u) modes. The B,, mode at 121cm-l includesa significant amount of Al-Cl, stretch and this may explain the high intensity of the corresponding line. The A, mode at 107 cm-l is a symmetric bending involving a motion of all atoms ; it has been described by several authors as an A1-A1 stretch, which seems to be correct from our normal mode coordinate calculation.The force constants obtained (table 3) demonstrate clearly that Fv(AIClb) is about 0.6 of Fv(AIC~,).~~* An estimate of the mean bond dissociation energies is l8 derived from our values by using Lippincot’s equation.26 We obtain : E(AlC1,) = 64.28 kcal mol-1 = 269 kJ mol-l E(MC1b) = 40.63kcal rno1-l = 170kJ mol-l. These values differ from those of ref. (27). The high value of fv(AICIb)-v(AIClb) (Cl common), together with the large difference between F6(AlCl,Al) and F8(clbA1clb), may be due to an important aluminium-aluminium interaction. Two A12C16 interaction force constants differ markedly from the AlCl, values : fva(A1C1,,) -w(AlC1,) and fva(A1C12 ,)-r(AlCl,). These two identical constants in AlCli take opposite values in A12C16, this finding implies (using internal coordinates) fR@--fkB = -(fd-fa which indicates a change in the relative values off andf’ from AlCl, to AIClb.INTERPRETATION AND RESULTS FROM THE CHLORINE ISOTOPIC FINE STRUCTURE The calculated patterns (fig. 2) are obtained by summing lorentzian curves for the 14 most abundant isotopic molecules (Ito XIV). The full width at half height is equal to the experimental slitwidth. The intensity of each component is proportional to the abundance of the Corresponding molecule. For each case, we have reproduced the experimental curves [fig.2(c) and (41. Curves (a)and (b)obtained from Maroni l1 and the AlClz force field 25 reproduce the frequency ranges but are not able to reproduce the isotopic shifts.This is the result of an inadequate set of interaction force constants. In addition to obtaining an accurate force field, the high resolution spectral analysis permits an unambiguous assignment of many of the stretching modes. Eesiecki and Shirk1 had proposed that the 320cm-l i.r. band originated in an impurity. Our result concerning the shape and the width of the corresponding absorption agrees with experimental data (fig. 2). The 320cm-l i.r. absorption is assigned to the ~17mode. Some doubt remained for the assignment of the V6BIg mode. Our results are reported for v6 at 285 cm-l. We have performed a calcula- tion with v6 at 318 cm-l ; this assignment was shown to be incorrect since a quite different shape is expected for the corresponding absorption. This would arise from a coupling effect which leads to a splitting of the nearest frequencies for numerous non-centrosymmetric molecules where v6 and ~17belong to the same symmetry species.Thus a negative value of fva(A1C1,,) -r(AlC1,) displaces the two VIBRATIONAL SPECTRA OF MATRIX ISOLATED A12C16 higher components of the 615cm-l i.r. mode. The calculated isotopic shift of 0.9 cm-l (1.1 crn-l obs.) implies a higher absolute value for this constant, but such a high value would lead to a splitting of both higher Components. We think that an interaction constant between v(AlC1,) and torsional motions should be necessary to give a better fit.Since the isotopic shiAs also depend on the geometry, we have used different values of the Cl,AlCI, angles in the calculation. The greatest influence occurs for the v,(A,) and v1,(B3J modes, while the vg and v16 absorption shapes rem.a.in un-perturbed. In both cases, a very high resolution study is necessary to explain the perturbations of the molecular geometry induced by the matrix. 11.1'1.1.11.1 490 485 480 S/crn-l FIG.5.-High resolution i.r. spectrum of A12C16in argon matrix in the q6 region. (d)Experimentalfrom chlorineisotopes in natural abundancy. (e) Combination of three (f)patterns using for each of them the frequencies and relative intensities issued from experimental curve (9). (f) Theoretical pattern summing 14 lorentzian curves from the 14 most abundant molecuh in a natural abundancy sample.(8) Schnockel's experimental data from a 35Clenriched sample. The resolutions in (d)-(f)are 0.6 cm-l. All three bands of spectrum (9)are assumed to be Av+ = 0.6 cm-I which is an approximate value for the central peak. M. TRANQUILLE AND M. POUASSIER Finally, we have calculated new profiles by mixing the calculated isotopic patterns in order to simulate “environment effects ”. The 425 cm-l band shows a triplet structure. The relative intensities of its com- ponents are not the same in argon and nitrogen matrices. In the latter, the intensities are closer to the expected ratio. For the argon triplet, where the central peak is the most intense, we caa explain the intensities by mixing two isotopic patterns removed by one isotopic shift (e.g., 2.1 cm-l).In fig.5, we have reported the simulation of the “ environment effects ” for the 485 cm-l i.r. band in an argon matrix. An actual calculation is possible from the experimental results of Schnockel obtained with 95 % 35Cl enriched samples. This author has observed a triplet [fig. 5(g)J. We have calculated the areas of these peaks to give the intensity ratios between the three isotopic patterns (b)in order to simulate the experimental result for natural abundance (d). The resulting spectrum (e) demonstrates fiat “environment effects ” are the same in the two experiments but it indicates the limits of interpreting many results when such effects occur.TABLE5.-THEWODYNAMIC DATA All values are expressed in cal mo1-I K-l s;(Aa) S;(Al*C16) As$(A12C16 + 2AlC13)T/K statistical calorimetric statistical Catorimetric statistical calorimetric a b b 75.2 35.6e 298 74.8 75.6c 104.7(112.7) 113.8 44.9(36.9) 36.2e 77.0d 112.8 37.6 740 31.ge 32.7e 32.0f 750 91.a 140.5(150.3) 43.1(33.3) 775 35.2= 31.7e aoo 93.1 143.1( 153.1) 43.1(33.1) 817 33.6 982 104.6d 1000 97.4 152.2(162.7) 42.6(32.1) IDEALGAS THERMODYNAMIC FUNCTIONS FOR A12Cls T/K G Ho-HH,”IT SO -(Go-HG)]T 298.15 37.9 27.03 112.7 85.67 400 40.2 30.12 124.2 94.07 600 42.0 33.83 140.9 107.06 800 42.7 35.97 153.1 117.11 1000 43.1 37.36 162.7 125.30 1500 43.4 39.34 180.2 140.87 a From wavenumbers of ref.(4). Left-hand column : calculated from 17 frequenciesnot including vl0. The wavenumbers are those of the trapped gas spectra plus the calculated twisting modes. Right-hand column : 18 vibrational frequencies including vlo = 10 cm-l. The calorimetric values are those of ref. (28) except ref. (29), dref. (30), eref. 31 and fref. (32). VIBRATIONAL SPECTRA OF MATRIX ISOLATED Al2C16 For the 615 cm-l band in argon, the lack of a precise result from 35Cl enrichment makes similar work very difficult. The shape obtained is similar to Beattie’s experi- ment.2 All attempts to deconvolute the corresponding pattern have failed because it presents a badly resolved tail. On the basis of the isotopic shifts, we propose three components commencing at 621.4, 619.25 and 618.85 cm-l due to ‘‘ environment effects ” on A12C16, but the presence of a trace of monomer cannot be excluded because the corresponding nitrogen matrix does show very weak absorption in the “monomer ” region.THERMODYNAMIC FUNCTIONS Knowing the 17 frequencies, including the calculated twisting modes, permits one to determine the magnitude of the remaining unknown wavenumber of the vl0 ring-puckering mode using the absolute entropy deduced from calorimetric data. Two methods can be used to compare statistical values and experimental data: (i) Use only the vibrational frequencies of the dimer to calculate s;(A12C16) and compare with the corresponding value from calorimetric data. (ii) The frequencies of the monomer and dimer molecules lead to s$(AlCl,) and s;(A12C16), e.g.,ds;(Al2Cl6 +2AlC13); this difference is compared with the calorimetric value directly obtained from vapour pressure data. The results axe presented in table 5.The statistical values are obtained from Shirk’s frequencies for AlCl, and the calculated wavenumbers in the present work for A12C16. The best fit is obtained if we take the vlo mode at 1Ocm-l. This wavenumber would be slightly higher if we took into account the fact that the experi- mental data contain a mixing entropy which is w 1.1 and 1.4 e.u. for AlCl, and A12C16, respectively. CONCLUSION This work provides a better understanding of the A12C16 vibrational spectrum. The matrix isolation technique applied to ix., far-ir.and Ranaan spectroscopies is successful in obtaining isotopic patterns from many stretching modes. The observa- tion of a new absorption at 135 cm-l assists the determination of 15 vibrational frequencies of A12C16. These experimental results lead to an accurate force field for this bridged dimer molecule. The bridging bond energies and stretching force constants are z 0.6 of the corresponding terminal bond values. The Al-CI, force constant, equal to 2.26 mdyn is intermediate between 2.0 and 2.74 mdyn A-l found for A1-C1 bonds, respectively, in AlCl, and AlC13. Using thermodynamic data, we expect the unobserved v1 ring-puckering mode to occur at the very low frequency of = 10 cm-l. In this work, we have also illustrated the difficulty in interpreting the splittings on the matrix spectra due to “environment effects ”.In the case of argon, they make the interpretation of numerous isotopic patterns impossible. However, the use of different matrix materials may be helpful in eliminating such an obstacle. When this has no effect, isotopic enrichment is necessary as an intermediate in the analysis of the spectra. We thank Dr. Hg Schnockel for the communication of his unpublished results and Messrs G. Daleau and J. C. Cornut for their technical assistance. M. L. Lesiecki and J. S. Shirk, J. Chem. Phyx., 1972, 56, 4171. I. R. Beattie, H. E. Blayden, S. M. Hall, S. N. Jenny and J. S. Ogden, J.C.S. Dalton, 1976,666. M. TRANQUILLE AND M. FOUASSIER V. Hg. Schnockel, 2.anorg. Chem., 1976,424,203.R. G. S. Pong, A. E. Shirk and J. S.Shirk, Ber. Bunsenges. phys. Chem., 1978,82,79.’K. J. Palmer and N. Elliott, J. Amer. Chem. Soc., 1938, 60,1852. V. H. Brode, Ann. Phys., 1940,5,344.’P. A. Akishin, N. G. Rambidi and E. Z. Zasorin, Soviet Phys. Cryst., 1959, 4, 167. R. L. Harris, R. E. Wood and H. L. Ritter, J. Amer. Chem. Soc., 1951, 73, 3151. R. P. Bell and H. C. Longuet-Higgins,Proc. Roy. SOC.A, 1945, 183, 357. lo H. Gerding and E. Smit, Z. phys. Chem. (Leipz&), 1941, B50,171. l1 V. A. Maroni, D. M. Gruen, R. L. McBeth and E. J. Cairns, Spectrochim. Acta, 1970,26A, 418. l2 I. R. Beattie and J. R. Horder, J. Chem. SOC. A, 1969,2655. G. Torsi, G. Mamantov and G. M. Begun, Inorg. Nuclear Chem. Letters, 1970, 6, 553. l4 W.Klemperer, J. Chem. Phys., 1956. 24, 353. l5 P. A. Perov, S.V. Nedyak and A. A. Mal’tsev, Vest. Moskov. Univ. Khim., 1974,29,201. l6 R. H. Miller, Jr., Ph.D. Thesis (Ohio University, Athens, Ohio, 1965). l7 T. Onishi and T. Shimanouchi, Spectrochim. Acta, 1964,20,325. K. Venkateswarlu and A. Natarajan, Acta Phys. Polon., 1967, t32,205. l9 Y.Grenie and J. C. Lassegues, Rev. G.A.M.S., 1971,3,254. ‘O Tables of Wavenumbers for the Calibration of I.R. Spectrometers: Parts 111 and IV,Pure Appl. Chem., 1973,33,620. 21 J. A. A. Ketelaar, Z. Krist., 1935,90,237 ; K. Sasvari, Acta Phys. Acad. Sci. Hung., 1958,9,195. 22 E. V. Pershina and Sh Sh. Raskin, Uptics and Spectroscopy, 1962,13,272. 23 E. B. Wilson, Jr., J. C. Decius and P. C. Cross, Molecular Vibrations (McGraw-Hill, New York, 1955).24 M. Tranquille, Th2se (Bordeaux, 1975), (C.N.R.S. no. A.O. 5315) ;J. Derouault, M. T. Forel and P. Maraval, Canud. Spectr., 1978,23, 67. 25 J. Derouault and M. T. Forel, Ann. Chim. (France), 1971, 6, 131. 26 E. R. Lippincott and R. Schroeder,J. Amer. Chem. SOC.,1956,78,5171. ”K. Wade, J. Chem. Educ., 1972,49,502. 28 L. D. Polyachenok, G. D. Dudchik and 0. G. Polyachenok, Russ. J. Phys. Chem., 1976, 50, 227, transl. from Zhur. jiz. Khim., 1976, 50, 387. 29 V. B. Nesterenko, A. V. Zinovev and M. A. Bazhin, Vest. Akad. Navuk. Belarus. S.S.R. Sir. Fiz., 1967, No. 2, 32. 30 M. A. Frisch, M. A. Greenbaum and M. Farber, J. Phys. Chem., 1965,69,3001. 31 G. E. Vrieland and D. R. Stull, J. Chem. Eng. Data, 1967, 12, 532. 32 A. Smits and J. L. Meijering,2.phys. Chem. (Leipzig), 1938, B41,98. (PAPER 8/2207)

ISSN:0300-9238    

DOI:10.1039/F29807600026

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

J.C.S. Faraday 11, 1980, 76,4248 Study of Self-associationof t-Butyl Alcohol by Linear and Non-linear Dielectric Effects BY JERZYMALECKI," STEFANIA AND JADWIGA NOWAKBALANICKA Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17/19,60-179 Poznari, Poland Received 9th February, 1979 A method for the simultaneous determination of three independent values of the free energy of self-association from experimental dielectric data is proposed. This involves the determination of AG, AH and AS for linear bond formation in open multimers, for bond formation in cyclic trimers and in higher cyclic multimers of t-butanol. The proposed method allows one to evaluate the relative concentrations of open and cyclic structures with great accuracy. Moreover, it can determine which of the possible models of association describes the experimental system being tested.Studies of self-association of alcohols as well as of phenols, amides, water and other compounds meet with numerous difficulties, which stem mainly from the simultaneous presence in the solution of many associates, such as monomers, dimers, trimers etc. Moreover, these associates may occur in various spatial configurations, among which chain (open) and cyclic structures where the hydrogen bond forms a closed ring are distinguished. In order to describe such a system it is necessary to introduce many parameters, whereas experiment normally gives at best one or two mean values only. As a result, the determination of these parameters is not unequivocal, or at least is burdened with errors coming from the simplified model used.An extreme example is the Mecke-Kempter model which treats all the hydrogen bonds that are formed identically and radically reduces the number of para- meters to a single mean free energy AG of the hydrogen bond. One possible solution to this complicated problem is to utilize info'rmation from several experimental methods. As a rule, each method in addition to new ex-peri- mental data will also introduce new molecular paxanieters essential to a proper description. Unfortunately, literature data on the process of self-association, and in particular on the constants of self-association and on thermodynamic functions, are discordant and give only a general picture of the process.The aim of this work was to obtain exact data describing the self-association of solutions of t-butyl alcohol in cyclohexane over the whole range of concentration. Use was made of data from two dielectric methods, namely from experimental determination of the mean square of the dipole moment (F2) and from studies on the non-linear dielectric effect (NDE) which is described by the value of Ae/E2, where Ahe denotes the change of electric permittivity of the medium caused by the application of strong electric field of intensity E.2-4 Non-linear dielectric effects are sensitive specifically to molecular association because the application of a strong electric field slightly shifts molecular equilibria to favour those complexes with a greater dipole moment.Modern electronic^,^ which ensures great accuracy in measuring changes of electrical permittivity, allows the study of this phenomenon. At the same time there exists a simple general 42 J. MALECKI, S. BALANICKA AND J. NOWAK theory which relates the measured values of ji2 and A&/E2with molecular para- meters, such as the dipole moments of associates (pi) and the free energies of inter- molecular interaction (AG). EXPERIMENTAL Experimental studies were carried out with solutions of t-butyl alcohol in cyclohexane at five different temperatures in the range 293-328 K over the whole range of concentra- tions. To measure the value of A&/E2the apparatus described in ref. (5) was used.Measurements were performed in the condenser with careful thermostatting, providing stability of temperature to within 0.1 K. Reagents were carefully dried and distilled before measurement. The values for jiz were calculated on the basis of the precise data published by H~yskens.~ ASSUMPTIONS AND ALGORITHM OF CALCULATIONS In order to determine from experimental data the energies of hydrogen bonds responsible for self-association of t-butyl alcohol, we used the NDE theory elaborated by one of the authors of the present paper.6 The basic relations expressing ji2 and As/E2as functions of molecular parameters are as follows : and where the summation over i includes all L kinds of associates present in the solution. pi denotes the dipole moment of the complex containing i molecules, xi= iNt/N2, its concentration defined by the number of complexes Niand the number of investigated molecules N2, and f = N2/Ndenotes the concentration expressed as mole fraction.The function B(E,n2, V)depends on the choice of the local field Fand for Onsager’s model used here it is expressed by : ~~+2)4 n~ (3)B(E,n2, V) = (2c2 +n4)(2&+ ( n2)2i/ where n denotes the refractive index of the smple and Y its molar volume. The values A and S1denote constants equal to A=-N and S1= As/E2 45&,k3T B(E1Y n:, Vl) (4) where E~ denotes the electrical permittivity of a vacuum, the subscript “ 1” refers to values characterizing the solvent, Nis Avogadro’s constant, k Boltzmann’s constant and T the absolute temperature.Quantities yf axiyi = 6k2T2-xi a(F2) we have to find by solving a set of equations in which L-1has the form SELF-ASSOCIATION OF t-BUTYL ALCOHOL and one equation cxiy, = 0 (7)i resulting from the mass conservation law. Each of the eqn (6) is related with one of the chemical equilibria assumed for the full description of the process of association : mlAl+m2A2+ .. . + m,At+m,+lA,,l+ .. .. (8) The right-hand coefficients m,in process (8) are positive and the left hand ones negative. Further details can be found in ref. (6). In order to describe the self-association of alcohols we tested models with selected kinds of multimers frequently used for this purpose, 9-1 e.g., monomer-dimer-trimer, monomer-trimer-octamer or monomer-linear-tetramer-cyclic-tetramer. None of the models was able to reproduce the experimental dependence of the A&/E2(f), giving disagreement not only in order of magnitude but even in the sign.Accordingly we used a more general description of the self-association of t-butyl alcohol intro- ducing three parameters : namely AGO,the free enthalpy for linear bonds in open niultimers, AG,, a corresponding enthalpy for cyclic hydrogen bonds in tetramers and higher multimers, and AGSc, the free enthalpy for bonds in cyclic trimers. The number of the above mentioned parameters was limited to three. Under these conditions the applied procedure is unequivocal. In the first stage of the calculations assumed values of AG for the corresponding react ions A, +&-I + AL are introduced. The AG values are used for the calculation of multimer equilibrium constants Kf: Ki = exp [ -(i-l)AG,/RT]+exp (-iAGc/RT) (9) and concentrations of multimers xi.To do this, a concrete thermodynamic model should be assumed. Calculations were performed for several models, such as the model of ideal association, the athermal (Flory) model and the model where multimer activities are expressed in terms of their molar concentrations. Over a broad range of concentration alternative representations of thermodynamic activity functions lead to rather serious differences (up to 100 %) in theoretical ji2(Cf)and A&/E2(Cf) dependences as compared with experiment. The best results, given in this paper, were achieved with a model of ideal association.In the next stage of calculation one requires the dipole moments (pf) for all the multimers taken into consideration in the model. Unfortunately experimental determination of the piseparately for each multimer is not possible, so we assumed that the dipole moments of multimers result from their geometry. Such a procedure introduces an uncertainty in pi values and consequently a systematic error in the AG values which is discussed below. For a given set of the piparameters we can easily calculate values y, by solving the set of eqn (6) and (7) and subsequently can determine the theoretical values jiz and A&/E2. In each case, calculations were made over the whale accessible range of concentrations with a step equal to 0.1 m.f.(mol fraction). The set of theoretical values jZ2 and A&/E2allows us to calculate the relative deviations from experimental values [for example 6jZ2 = (jZzxp-,ii&eor)/jZ~xp]and to determine the mean total error 6Rfor the whole range of concentrations : J. MALECKI, S. BALANICKA AND J. NOWAK 45 The error is determined each time for a given set of parameters AGO, AG, and AG3, and the calculations are made in the assumed ranges and steps for each of the three above mentioned parameters. Finally, a four-dimensional map of errors is obtained. The last stage of the calculation consists of finding the minimum of the function GR(AGo,AG,, AG3,) and printing out the results. The program was written in FORTRAN 1900 and the calculations were executed by means of an ODRA 1305 computer.It should be noted that the proposed method of determining the three parameters consists of the simultaneous comparison of two functions ji2(f) and A&/E2(f)with the theoretical ones in a wide range of concentrations. For the given set of para- meters pi the method is unequivocal, even to the point of being critical. RESULTS AND DISCUSSION Calculations according to the algorithm described above were performed for experimental data (F2 and A&/E2)obtained for solutions of t-butyl alcohol in cyclo- hexane in the concentration range 0.1-0.9 m.f. at temperatures 293, 298, 308, 318 and 328 K. The results of calculations are presented in fig. 1 and 2, which compare the experimental points with the theoretical dependence of optimum fit drawn as a continuous line.The optimum fit should be considered as a compromise in minimizing deviations simultaneously for an appropriate pair of functions ,E2 and A&IE2in the whole range of concentrations. The free enthalpies AG determined in this way axe shown in table 1. These values were used to calculate the enthalpies (AH) and entropies (AS) of hydrogen bonds. Fig. 3 illustrates the respective dependences of AG/T on l/T. i 70 -6 60 -5 50 -4? 40V 0 rgI -3 41 30\ N 15 -220 -1'lo 0 0.2 0.4 0.6 0.8 f f FIG. l.-Opthum fit of theoretical values of p2 and Ac/E2(continuous lines) to experimental data for T = e, 293 ; 0,308 and x ,328 K.46 SELF-ASSOCIATION OF f-BUTYL ALCOHOL Lt is difficult to compare our results with literature data because of the differences both in the range of concentration and the models applied. Most of the accessible data, have been obtained from n.m.r. and infrared spectra using highly simplified or highly unlikely models of self-association. It is possible to state, however, that the values AG B -8 kJ mol-1 seem to be reasonable when compared with other results. On the other hand, the value -AH w 30 kJ mol-1 seems to be large. There are many exact data concerning the enthalpies and entropies of hydrogen bonds of the type OH. . . 0, but as a rule these did not originate from studies on the self- associationof alcohols. On the basis of these data one can assume that the enthalpy 70 -6 60 -5 so NE -4 5 40 p3 230 -3 ih pb 1 \ n% -2 420 10 I 1 I I J I 0.2 0.4 0.6 0.8 f FIG.2.-Optimwn fit of theoretical values of b2and Ac/E2(continuous lines) to experimental data for T= 0,298 and 0,318 K.TABLE1.INTERMOLECULAR ENERGIES OF HYDROGEN BONDS IN ASSOCIATES OF f-BUTYL ALCOHOL -AG(+0.4)/kJ mol-l 293 298 T/K 308 318 328 -AW(+9)/kJmbl-l -AS(+30) /JK-l mol-1 ~~ ~ linear bonds 9.2 8.8 7.9 7.1 6.3 34 83 cyclic bonds i>,4 cyclic bonds in trimers 8.1 7.4 7.7 7.0 6.9 6.4 6.2 5.5 5.4 4.9 31 29 77 72 i= 3 J. MAEECKI, S. BALANICKA AND J. NOWAK for bonds OH. . . 0 in alcohols does not exceed 25 kJ mol-l.This divergence is probably due to the fact that there exists a weak temperature dependence of the dipole moments of multimers resulting from their non-rigidity. Unfortunately, without additional, independent data this phenomenon cannot be taken into account in the applied procedure. 103 KIT FIG.3.-AG/Tplotted against l/Tfor linear and cyclic bonds in t-butanol. (a)AGOIT;(b) AGc/T;(4 AG3cIT. Another source of the divergence could originate in the broad range of con- centration (0.1-0.9m.f.) over which we attempted to fit the data. The whole physical character of the medium, which can be expressed by means of activity coefficients, changes with concentration. On the other hand the broader the con- centration range used the more unequivocal and detailed the picture obtained.From this point of view we rejected only the low concentrations (below 0.1 m.f.) as well as high concentrations (above 0.9 m.f.) where the activity coefficients change most critically. Nevertheless, this compromise can affect on the final results, particularly the AH and AS values. The method proposed here provides substantial information on the self-association process in alcohols. The main source of error is the uncertainty in the dipole moments pi of multimers. Assuming that this uncertainty is of the order of 30 % the resulting systematic error in AG values mounts to 20 %. It is worth stressing the specific nature of this method, which allows one to evaluate with great accuracy the relative concentrations of cyclic and open structures. The ratio AGJAG,, SELF-ASSOCIATION OF t-BUTYL ALCOHOL depends but weakly on the assumed values of pi.Taking into account again the 30 % error in pi the accuracy of determining the ratio AG,/AGo is of the order of 1 %. An important feature of the method is the possibility it provides for a simul-taneous determination of the three parameters AG. Neither is the selection of the three parameters left to individual choice, which means that we can decide which of the possible models of association is able best to describe the experimental system being tested. H. Kempter and R. Mecke, 2.phys. Chem., 1941, 43, 229. F. Kautzsch, Phys. Z., 1928,29,105. A. Piekara, Acta Phys. Polon., 1950, 10, 37, 107. J. Matecki, Acta Phys. Polon., 1962, 21, 13 ; J. Chem. Phys., 1962, 36, 2144; 1965, 43, 1351. J. Malecki, J.C.S. Faraday 11, 1976,72,1214. J. Matecki, J.C.S. Faraday 11, 1976,72, 104. 'P. Huyskens, R. Henry and G. Gillerot, Bull. SOC.chim. France, 1962, 720. L. Onsager, J. Amer. Chem. SOC.,1936,543,1486. E. E. Tucker, S. B. Farnham and S. D. Christian, J. Phys. Chem., 1959,73,3820. loA. N. Fletcher and C. A. Heller, J. Phys. Chem., 1967, 71, 3742. l1 A. N. Fletcher, J. Phys. Chem., 1969,73,2217; 1970,74,216. (PAPER 9/208)

ISSN:0300-9238    

DOI:10.1039/F29807600042

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

J.C.S. Faraday 11, 1980,76,49-66 Laser-induced Fluorescence of IBr : the B3JJ(O+)Excited State BY MICHAEL AND MICHAELA. A. CLYNE* C. HEAVEN Department of Chemistry, Queen Mary College, Mile End Road, London El 4NS Received 8th March, 1979 Quantum-resolved fluorescence from excited IBr B31T(O+)-X’Xf has been observed for the first the. A narrow-band pulsed dye laser, pumped by a doubled Nd-YAG laser, was used to excite IBr at wavelengths between 630 and 650nm. Excited-state vibrational levels with v’ 5 3 were observed to emit fluorescence ;all higher levels evidently were completely predissociated. The lifetimes T~ of resolved ro-vibrational states of IBr (B) with v’ = 2, 3 and 34 L J’ 2 0 were determined. Values for T~ decreased as a function of increasing J’ and were lower in the 0’ = 3 state than in the u’ = 2 state. All values of T~ were much shorter than the estimated radiative life- time, indicating that predissociation of moderate strength affects the v’ = 2 and v’ = 3 ro-vibrational manifolds.Both rotation-free and rotationally-dependent predissociations were present in IBr (B)and possible mechanisms for the predissociations are discussed. Brown was the first to show that iodine monobromide, IBr, possesses three distinct band systems in the visible and near infrared spectral regions (540-800 nm). Selin2 and Selin and Soderborg analysed the absorption spectrum of IBr at high resolution. They 2* showed that the shorter-wavelength bands were due to the B311(O+)-XIX+ and the B’(O+)-XIX+transitions, whilst the longer-wavelength bands were due to the A3];1(l) -XIZ+transition. Spectroscopic constants for some vibrational levels of the X, A, B and B’ states of IBr were reported, as a result of these Fig.1 shows the potential energy functions for the XIX+,B311(O+) and B‘(O+) states of 179Br. The A state, which dissociates to 12P3.+Br2P4 ground-state atoms, lies at energies below that of the B state. According to the classical representation of fig. 1, the B’(O+) state of IBr is formed by the avoided crossing of the repulsive O+ state with the higher vibrational levels (u‘ 2 5) of the B311(O+)state. The B‘-X bands possess fragmentary structures le3and only a limited number of sharp rota- tional lines axe observed.2 Child4 has interpreted the variations in IBr linewidths of the B’-X bands in terms of a coupling of intermediate strength between the B state and the O+ state.The energy and internuclear distance for the crossing point between the B state and the O+ state have been derived by Child and Bernsteins and later amended by Child.4 Two distinct previous studies of laser-induced fluorescence (LIF) in IBr have been Weinstock ti and Weinstock and Preston excited the predissociated levels of the B’ states of 179Br and PBr, using a single-mode C.W. dye laser. The fluorescence spectra showed long progressions of bands in the ground-state vibrational quantum number (u” = 0-19). Improved constants for the ground XIC+state were obtained, but no data on the lifetime of the B’ state were reported.6- Wright and Havey * used broad-band excitation, with 150 ns duration pulses from a dye laser, to excite fluorescence in IBr.It was not possible to assign the 49 LASER-INDUCED FLUORESCENCE OF IBr 2 3 4 5 6 rlA FIG.1.-Morse potential energy functions for IBr. Note that the weakly-bound B'(O+) state is formed by interaction of the bound B311(O+)and the repulsive O+ states. All bound levels of the B and B' states lie at energies in excess of that for ground-state "P++'P+ atoms. quantum state of the emitting IBr;8 however, Wright and Havey* reported a collision-free lifetime T~ = (0.54+0.05) p,which they assumed was for the v' = 2, 3 and 4 levels of IBr B311(O+) In the present work a novel narrow-band pulsed laser (M 10 ns duration) operated in the red (A NN 640 nm) has been used to excite quantum-resolved (u', J') states of IBr (B) for the first time.Strong dependences of lifetime upon vibrational (u') and rotational (J') quantum numbers were found; all states studied (v = 2,3) were pre-dissociated. There is almost no agreement of the present zo determinations with those of Wright and Havey,8 as might be expected in view of the impossibility of exciting a single quantum state in their work. EXPERIMENTAL NARROW-BAND DYE LASER TUNABLE IN THE RED Low pressures (1-5 mTorr) of iodine monobromide were excited using a narrow-band dye laser which was tunable in the red. A pressure-tuned dye oscillator was used to generate low-power7 but spectrally-pure radiation.This oscillator incorporated an echelle grating and an air-spaced etalon and was essentially identical with the pressure-tuned dye laser described by Clyne and Heaven.' However, in our previous work on Br2,' the dye laser gave output pulses whose wavelength was tunable only up to 600 nm. In the present work, 30 % of the energy (w5 mJ per pulse) from a frequency-doubled Nd-YAG laser was used to pump the dye oscillator longitudinally. Because ofthe relatively M. A. A. CLYNE AND M. C. HEAVEN small Stokes frequency shift between the exciting wavelength (532 nm) and the fluorescence of available red dyes, tunable laser radiation could be obtained up to at least 650 nm. With a 2 x mol dm-3 methanolic solution of Cresyl Violet Perchlorate (Exciton Inc., CVP), the laser wavelength could be tuned from 615 to 650 nm.Shorter wavelengths were accessible using Rhodamine B in methanol. dye oscillator t M4 bl DM l-----l Pr M2 amplifier M3 L3?J4M4 FIG.2.-Schematic diagram of the dye oscillator-amplifier laser, pumped by a doubled Nd-YAG laser. MI, beam splitting mirror (30 % transmission);L1, lens to focus pump beam into dye cell DC1 of oscil- lator ;DM, dichroic mirror, 99 % reflective at 580 nm, 80 % transmissive at 532 nm ;F, air-spacedFabry-Perot etalon ;G, echelle grating ;Pry pressure chamber ;M2, dye-oscillator front mirror ;M3, M4, 99 % reflectors ; L2, L3, focusing lenses ; P, reflecting prism ; Al, A2 apertures ;DC2, dye amplifier flowing cell.All lenses and prisms A.R. coated (single layer MgF2). Sources :M1,DM, CVI Inc., Albuquerque, New Mexico ;Ll-L3, P, Optical Works Ltd ;F, M2, Technical Optics Ltd ; G, Bausch and Lomb Inc. ;Pr, Leisk Engineering Ltd ;DC1, Molectron Corp ;M3, M4, NewportResearch Corp. ;YAG laser, JK Lasers Ltd. Fig. 2 shows a schematic of the dye oscillator pumped by a Nd-YAG laser (JK Lasers System 2000). The Nd-YAG laser was Q-switched and gave 15ns pulses of energy 2 100 mJ at 1.064pm and 5 20 mJ at 532 nm. Also shown in fig. 2 is the dye amplifier, which was used to increase the energy of the spectrally-pure, but low-power pulses from the dye oscillator. A beam splitter, a reflecting prism and a lens were used to direct 70 % of the 532 nm pump energy into a flowing dye cell, which acted as a dye amplifier.Apertures were placed in the optical path, in order to minimize amplification of the rather divergent super- radiance. Details of the entire dye oscillator-amplifier system and its performance tests are given elsewhere. O In summary, tests for spectral purity (bandwidth) and for output power with Rhodamine 6G were carried out. Rhodamine 6G, Rhodamine B and Cresyl Violet Perchlorate gave single-frequency output under the conditions used, with a mean bandwidth better than 1pm, as determined interferometrically. Output energy of 0.1 mJ per pulse (mean time-averaged power M 4 mW at 40Hz repetition rate) was obtained from the dye oscillator at 560 nm. After amplification, the pulse energy was 2mJ (80mW time-averaged power), with no degradation of bandwidth.Output energy with Cresyl Violet Perchlorate was about a factor of two lower. Both shot-to-shot fluctuations (< 10 %) and frequency stability were LASER-INDUCED FLUORESCENCE OF iBr greatly superior to those of the dye laser pumped by a N2laser. Pulse energy of the dye laser pumped by the N2laser was about 5 puJ using Rhodamine 6G.9 FLUORESCENCE CELL AND DETECTION SYSTEM As before, the dye laser beam was steered and focused to a waist at the centre of a baffled fluorescence cell (fig. 3). All metal surfaces inside the cell were coated with matt black Teflon. The cell (30mm in diameter) constituted part of a flow system, through which small flows of IBr were passed. Pumping was by means of a trapped mercury diffusion pump ;total pressure was measured with a monel capacitance manometer (10-10-5Torr, MKS Baratron model 310).Fluorescent light was collected over a 1.6sr solid angle using a pair of aspheric glass lenses ;glass cut-off filters were used to block stray laser light. The detector was a fast high- gain S20 photomultiplier tube (EM1 9816B, 44 mm cathode, 2 ns rise time). (a) gas flow 1 brewster angle on exit window I\ 4 'observation fluorescence port l aser axis 1 ( photomultiplier gas flow 'aspheric lens FIG.3.-Fluorescence cell for laser excitation of IBr. Plan (a)and section (b) of fluorescence cell. Note light collection system with two f10.65 aspheric lenses. LASER EXCITATION SPECTRA As in previous work,1° laser excitation spectra were obtained by recording undispersed fluorescence intensity as a function of laser wavelength.A boxcar integrator with a gatewidth of 2 ps was used to average the integrated intensity resulting from a number of laser pulses. Because of the use of a pressure-tuned dye oscillator, the laser excitation spectra showed exactly linear wavelength scans,1°with no detectable change in dispersion across each scan M. A. A. CLYNE AND M. C. HEAVEN of approximately 0.3-0.4 nm. The scan gas was N2,used from vacuum to 2 atm pres- sure.l0 Absolute wavelengths were measured to 20.05 nm using a 1m grating mono- chromat or. LIFETIME MEASUREMENTS OF IBr (B) Selected (v’,J‘)levels in the B state manifold of IBr were papulated by tuning the laser to a suitable absorption line in the excitation spectrum.The resulting fluorescence decay curve following a laser pulse was recorded with the fast photomultiplier and a fast transient recorder (Biomation 6500, 2 ns per channel). The transient recorder was interfaced to the averager section of a mini-computer (Nicolet LABSO), in order to form an averaged decay curve resulting from many laser pulses, usually 1000in all. The averaged data were stored on disc in their exponential forms and were processed in batches under software control, in order to give the relevant lifetimes. Logarithmic decay curves could be obtained using the signal-averager programme and these were used to verify that the decay was strictly first- order with a single value of lifetime.The procedures were similar to those described in detail in earlier work,l’ except that both the photomultiplier and the transient recorder were faster. With the present system, duration of the laser pulse limited the shortest lifetime that could be measured to M 25 ns, compared with M 40 ns in previous work.ll IODINE MONOBROMIDE IBr is appreciably dissociated at equilibrium to I2and Br2 in the gas phase at 298 K : IBr +$I2+i5.Br2. I2 (B-X) fluorescence is extremely intense,12 whilst Br2 (B-X) fluorescence is of medium inten~ity.~J~Preliminary experiments with IBr which was taken directly from a trap (Hopkin and Williams, 98 %) showed laser excitation spectra of I2(B-X), with some additional lines not due to I2 or Br2.In order to suppress iodine formation in the equilibrium, bromine in metered amounts was distilled into the IBr and the laser excitation spectrum of the mixture was again obtained. By adjustment of the amount of added Br2, it was found possible to obtain a spectrum of IBr (B-X) in fluorescence which was free of I2(B-X) lines and which showed only weak Br (B-X) lines. Comparison spectra of IZand Br2 in the 640 nm wave- length region were recorded separately. RESULTS KKR TURNING POINTS AND FRANCK-CONDONFACTORS FOR IBr (B-X) Since publication of our calculations of RKR turning points and Franck-Condon factors (q”,,vtt) for the B-X transition of IBr,13 new molecular constants have become available for the ground state, from the work of Weinstock and Pre~ton.~ These workers extended the calculations up to vn = 19 ; a considerable extrapolation to v” = 50 can be made now more confidently, in order to evaluate ij (see below).Excellent agreement between the present calculations of RKR turning points with thuse of Weinstock and Preston7 were obtained for the 179Br species. However, discrepancies were noted for the 181Br species :(a)the turning points are systematically ~~0.02A lower than those of Weinstock and Preston ;7 (b)the vibrational term values slowly diverge from agreement at low v” to a difference of ~9 cm-l for v” = 19. We axe of the opinion that Weinstock and Preston inadvertently used the reduced mass for I79Br in their I81Br calculations, since correction in this way resulted in close agree- ment with our turning points for 181Br.The reason for the discrepancy in the vibrational term values is not known. The RKR turning points for the XIZ+and B3n(O+)states of 179Br and 18%r are given in table 1. A slight discrepancy is noted with the tabulation of Clyne and McDermid l3 (for v” < 7), who inadvertently used one erruneous vibrational term value in their calculation. The agreement is good, in general. LASER-INDUCEDFLUORESCENCEOFIBr TABLEI.-RKR TURNING POINTS FOR IBr XIZ+ 0 134.2 2.4203 2.5220 133.1 2.4203 2.5216 1 401.2 2.3868 2.5634 398.1 2.3869 2.5628 2 666.6 2.3648 2.5934 661.5 2.3650 2.5927 3 930.3 2.3475 2.61 87 923.2 2.3477 2.6178 4 1192.4 2.3331 2.6414 1183.4 2.3333 2.6403 5 1452.8 2.3205 2.6622 141.8 2.3207 2.6610 6 1711.5 2.3093 2.6818 1698.7 2.3094 2.6804 7 1968.5 2.2992 2.7004 1953.8 2.2992 2.6989 8 2223.9 2.2899 2.71 83 2207.3 2.2899 2.7165 9 2477.5 2.2814 2.7355 2459.1 2.28 13 2.7335 10 2729.4 2.2735 2.7522 2709.2 2.2733 2.7500 11 2979.6 2.2661 2.7685 2957.6 2.2657 2.7661 12 3228.1 2.2592 2.7845 3204.2 2.2587 2.7818 13 3474.8 2.2526 2.8001 3449.2 2.2520 2.7972 14 15 3719.7 3962.9 2,2465 2.2406 2.8156 2.8308 3692.5 3933.9 2.%57 2.2396 2.8123 2.8273 16 4204.2 2.2351 2.8458 4173.6 2.2339 2.8420 17 4443.8 2.2298 2.8607 4411.6 2.2256 2.8538 18 4681.5 2.2247 2.8754 4647.8 2.2191 2.8670 19 4917.3 2.2199 2.8901 4882.2 2.2173 2.8845 20 5151.3 2.2153 2.9047 51 14.8 2.21 13 2.8975 RKR TUR NING POINTS FOR IB~~3n(o+) 179~r IS1Br 2, G(u) rmin rmax GW rminr max 0 70.6 2.7686 2.9090 70.0 2.7698 2.9097 1 207.5 2.7283 2.9759 206.0 2.7296 2.9762 2 338.4 2.7030 3.0291 335.9 2.7039 3.0286 3 462.4 2.6833 3.0779 459.1 2.6842 3.0771 4 579.0 2.6673 3.1264 574.9 2.6683 3.1255 5 687.5 2.6540 3.1769 682.7 2.6553 3.1759 G(u) values are in cm-l ;r,b and r,, are in A Coxon's prograd4 were used to calculate a matrix of Franck-Condon factors and the data for 20 3 Y" >, 0 and 5 2 v' 3 0 are presented in table 2.The data tabulated axe those for rotation-free states J' = J" = 0.T, was re-evaluated from Selin and Soderborg's data and the new ground-state constantsY6*' to be 16 168.4 cm-1 ; examination of Selin and Soderborg's data showed that their band origins could not be calculated correctly using their value T, = 16 165 cm-l. As expected, generally good agreement was obtained between the present qoe,factors and those given by Clyne and McDermid.13 Discrepancies average 20 % , with consistently lower qvr,uff values in the present work. However, values fur the u'-v" bands studied in the present work were close. The relevant 4".,,," values (Clyne and McDermid values l3 in parentheses) are as follows : 3-3 band, 9.0 x (13.4 x lo4);2-2 band, 5.0 x (7x ;2-3 band, 3.0 x (4.0 x loA). M. A.A. CLYNE AND M. C. HEAVEN TABLE2.-BAND ORIGINSlVaC ClIl-l, FRANCK-CONDON J’ = J” = 0r,-CENTROIDS/A FOR THE B3n(o+)-xlx+SYSTEM OF FACTORS (qv~upp) AND d/UN 0 1 2 3 4 5 6 16 104.84 15 837.83 15 572.44 15 308.71 15 046.64 14 786.25 14 527.53 4.-9 1 .-7 1 .-6 8.--6 O.OO0 05 0.000 20 0.000 72 2.625 8 2.638 6 2.651 3 2.664 0 2.676 8 2.689 6 2.702 5 16 241.84 15 974.79 15 709.40 15 445.67 15 183.60 14 923.21 14 664.49 5.-8 1 .-6 0.000 01 O.OO0 07 o.oO0 34 0.001 28 0.003 96 2.619 3 2.632 0 2.644 7 2.657 4 2.670 0 2.682 7 2.695 5 16 372.67 16 105.62 15 840.23 15 576.50 15 314.43 15 054.04 14 795.32 3 .-7 5 .-6 O.oO0 05 O.OO0 30 0.001 29 0.00430 0.011 36 2.613 0 2.625 7 2.638 4 2.651 0 2.663 6 2.676 3 2.688 9 16 496.72 16 229.67 15 964.28 15 700.55 15 438.48 15 178.09 14 919.37 1.-6 o.oO0 02 o.oO0 17 o.Oo0 90 0.003 44 0.009 96 0.022 35 2.607 1 2.619 5 2.632 4 2.645 0 2.657 6 2.670 2 2.682 7 16 613.31 16 346.26 16 080.87 15 817.14 15 555.07 15 294.68 15 035.96 3.-6 O.OO0 06 o.Oo0 44 0.002 11 0.007 12 0.017 79 0.033 51 2.601 6 2.614 2 2.626 9 2.639 4 2.651 9 2.664 4 2.676 9 16 721.77 164 54.72 16 189.33 15 925.60 15 663.53 15 403.14 15 144.42 o.oO0 01 O.OO0 14 0.000 95 0.004 04 0.012 02 0.025 81 0.043 32 2.596 4 2.609 1 2.621 7 2.634 2 2.646 7 2.659 1 2.671 5 V’/Vt‘ 7 8 9 10 11 12 13 0 14 270.50 14 015.16 13 761.53 13 509.60 13 259.40 13 010.95 12 764.24 0.002 16 0.005 50 0.012 19 0.023 68 0.040 56 0.062 17 0.085 19 2.715 4 2.728 6 2.741 9 2.755 3 2.769 1 2.783 0 2.792 2 1 14407.46 14 152.12 13 898.49 13 646.56 13 396.36 13 147.91 12 901.20 0.010 07 0.021 42 0.038 37 0.058 08 0.073 92 0.077 94 0.065 579 2.708 3 2.731 2 2.734 4 2.747 7 2.761 1 2.774 7 2.788 6 2 14 538.29 14 282.95 14 029.32 13 777.39 13 527.19 13 278.74 13 032.03 0.024 19 0.041 79 0.058 28 0.064 19 0.052 92 0.028 39 0.005 69 2.701 6 2.7144 2.727 3 2.7403 2.753 4 2.7664 2.778 2 3 14 662.34 14 407.00 14 153.37 13 901.44 13 651.24 13 402.79 13 156.08 0.039 21 0.053 31 0.054 17 0.037 33 0.012 75 0.000 04 0.010 43 2.695 3 2.707 9 2.720 6 2.733 2 2.745 3 2.718 5 2.776 7 4 14 778.93 14 523.59 14 269.96 14 018.03 13 767.83 13 519.38 13 272.67 0.047 32 0.048 06 0.031 12 0.008 24 0.000 37 0.014 92 0.033 88 2.689 4 2.701 8 2.714 2 2.725 7 2.752 4 2.755 8 2.768 3 5 14 887.39 14 632.05 14 378.42 14 126.49 13 876.29 13 627.84 13 381.13 0.04435 0.030 68 0.008 79 0.000 23 0.013 60 0.030 09 0.026 11 2.683 9 2.696 1 2.707 I 2.734 6 2.736 5 2.748 7 2.761 2 56 LASER-INDUCED FLUORESCENCE OF IBr TABLE2-continued V’]vn 14 15 16 17 18 19 20 0 12 519.30 12 276.40 12 034.78 11 795.25 11 557.55 11 321.71 11087.75 0.105 2 0.117 8 0.120 1 0.111 9 0.095 66 0.075 27 0.056 46 2.811 7 2.8265 2.841 4 2.8567 2.872 1 2.8878 2.903 9 1 12 656.26 12 413.10 12 171.74 11 932.21 11964.51 11 458.67 11 224.71 0.041 08 0.014 97 0.000 G5 0.005 68 0.028 00 0.057 61 0.082 49 2.8026 2.8163 2.8241 2.8509 2.8645 2.8795 2.8950 2 12 787.09 12 543.93 12 302.57 12 063.04 11 825.34 11 589.50 11 355.54 0.001 08 0.018 11 0.043 15 0.056 00 0.046 58 0.022 76 0.003 14 2.803 4 2.811 6 2.825 3 2.839 7 2.854 4 2.869 0 2.881 6 3 12 911.14 12 667.98 12 426.62 12 187.09 11.949.39 11 713.55 11479.59 0.033 09 0.044 05 0.031 33 0.008 54 0.000 38 0.016 04 0.040 21 2.789 1 2.802 6 2.816 3 2.829 3 2.860 2 2.863 8 2.878 1 4 13 027.73 12 784.57 12 543.21 12 303.68 12 065.98 11 830.14 11 596.18 0.033 23 0.013 43 0.000 06 0.010 86 0.0322 2 0.036 96 0.019 32 2.781 2 2.793 9 2.773 0 2.826 9 2.840 0 2.854 2 2.868 5 5 13 136.19 12 893.03 12 651.67 12 412.14 13 174.44 11 938.60 11 704.64 0.007 02 0.000 84 0.016 91 0.031 16 0.022 19 0.034 93 0.031 12 2.772 7 2.798 4 2.805 1 2.818 1 2.831 6 2.843 2 2.867 2 LASER EXCITATION SPECTRUM OF IBr (B-X) As may be seen from table 2, the Franck-Condon factors for transitions to 0’ < 5, which originate from the lowest vff ground-state levels, are very low.Thus, tran- sitions of IBr (B-X) which have the highest intensities in laser-induced fluorescence should be “hot bands ”, i.e., with vn > 0. Table 3 shows the Boltzmann populations 8,. of the vibrational levels vNof the ground X1Z+state of 179Br at 295 K. TABLE3.-BOLTZMANN POPULATIONS OF VIBRATIONAL LEVELS 2)’’ IN AT 295 K UN 0 1 2 3 4 5 eutr 0.727 0.197 0.0545 0.0154 0.0042 0.0012 Using the product qur,u88u+as an approximate measure of the intensity Iin laser- induced fluorescence, we deduce that these intensities of various 179Br B-X bands involving the upper state vf = 2 are as follows : 2-0, 2 x lo-’ ;2-1, 1.0 x ; 2-2, 2.7 x ;2-3,4.6 x ;2-4,5.4 x ;2-5,5.2 x Thus, the 2-3,2-4 and 2-5 bands may be predicted to be the most intense.The B-X transition of IBr resembles that of ICI,13 in that the hot bands are the most intense in laser-induced fluorescence. In light of these calculations, the wavelength region 630-645 nm was excited with the laser ;this is the range in which the most intense B-X bands of IBr may be expected. 57M. A. A. CLYNE AND M. C. HEAVEN Three B-X bands of the 179Br and TslBr isotopic species were observed in the laser excitation spectrum of pressures of 2-5 mTorr of iodine monobromide, ob-tained by recording undispersed fluorescence intensity, as a function of laser wave- length between 630 and 642nm. The bands were assigned as the 3-3, 2-2 and 2-3 transitions of IBr (B-X) ;parts of the structures of these bands are shown in fig.4. 3-3 BAND OF IBr (B-X) Rotational assignments of the 3-3 band were made by reference to Selin and Soderborg’s high resolution data from absorption spectroscopy. To confirm the rotational numbering, ground and excited-state combination differences were formed from our spectra and the resulting B, values were checked against those of Selin : 2* R(J)-P(J) = 4BJJ+ $) ; R(J-1)-P(J+ 1) = 4B,4J+ +). As shown in fig. 4, the two rotational branches P(J) and R(J) of each band can be followed clearly to the band origins, thus allowing the identification of lines with the lowest J-values.This complete resolution of the rotational structure allowed an unequivocal test of the rotational numbering to be made, thus confirming Selin and SiSderborg’s assignments for the 3-3 band. Our laser excitation spectra show much less overlapping of structure than the absorption spectra of Selin and Soderb~rg,~ who were unable to measure lines with J < 10 in any band whilst measurable lines in the 3-3 band were reported only for J 2 22. For heavy molecules, with incompletely-resolved rotational structures, it is normally difficult unequivocally to determine the numbering when only P and R branches are to be found, as in 31T(O+) -lZ+ transitions, and when no perturbations occur.Hence, the better resolution of the laser excitation spectra is particularly useful in setting the rotational numbering of the IBr bands. The region of maximum absorption intensity of the B-X bands of IBr is separated from that of the A311(l) -XIX+transitions. Convergence of the A-X band system occurs near 680 nm ;therefore no overlapping of the B-X bands by A-X bands is expected in the 630-650 nm wavelength region. The rotational intensity distribution in the 3-3 band is unusual (see fig. 4). It can be seen from fig. 4(a) that the intensities of lines near the band heads are anomalously high and examination of the complete laser excitation spectrum indicates the occur- rence of an intensity maximum near J” = 25. From the Boltzmann distribution for the ground state, rotational levels with a maximum intensity at J” = 42 would be expected.Lines with J”< 100 should possess sufficient intensity to be observable, but in fact no line with J” > 64 could be identified. The anomalous rotational distribution can be explained in terms of a rotationally-dependent predissociation, which is discussed below. 2-2 AND 2-3 BANDS OF IBr (B-X) The 2-2 and 2-3 bands of IBr (B-X) have not been reported previously ;however, these bands were readily identified in the laser excitation spectra, by comparison of the measured band head wavenumbers with those calculated from the constants. Fig. 4 shows the excitation spectra of the 2-2 and 2-3 bands. Assignments were based, as for the 3-3 band, upon combination differences for the ground and excited-states. As in the 3-3 band, the rotational intensity distributions in the 2-2 and 2-3 bands were peaked strongly towards low J’-values ; the highest J” transitions which were 1 I I I i 1 I 636.7 636.8 636.9 laser wavenumberlnrn 0 I I 1 I 1 1 I 641.7 641.8 641.9 laser wavenumber/cm-' M.A. A. CLYNE AND M. C. HEAVEN (4 I I I I I I I 63j.O 631.I 631.2 631.3 laser wavenumber/cm-l FIG.4.-Laser excitation spectra of IBr (B-X). Band width < 1pm. LBr pressure 2-5 mTorr. (a) The 3-3 bands near the 179Br and I8’Br band heads. Note extremely dense structure and low divergence of the (P and R) branches. (6) The 2-3 band head region. Note formation of well defined PR doublets in this band and very simple structure of the 18’Br head region.R branch lines of 18‘Br band are marked with spots. (c) The 2-2 band head region. Note weaker structure in this band and noticeable overlapping of Br2(B-X)rotational fines. identified were J”= 52 (2-2 band) and J” = 47 (2-3 band). Higher J” assignmentswere uncertain, because these weak lines were strongly overlapped by other bands of Br2 and IBr. 4-3 AND 4-4 BANDS OF IBr (B-X) The intensity factors for the 4-3 and 4-4 bands,which are expected to occur in the 630-650 nm region, are greater than those for the corresponding v’ = 3 bands. Thus I(4-3) = 3.2x and 1(4-4) = 3.0x in comparison with I(3-3) = 1.4x However, no rotational lines assignable to 0’ = 4 bands could be observed in laser-induced fluorescence. We estimate that the 4-3 band would have been observed if its intensity had been one-tenth of that of the 3-3 band.Thus, predissociation in v’ = 4 is evidentlyat least 20 times stronger than in v’ = 3, based on this observation and the calculated intensity factors. LIFETIME DETERMINATIONS IN IBr (B) The assigned laser excitation spectra (fig.4) were used to identify unblended roa tational lines in the 2-2 and 3-3 bands, which would be suitable for lifetime measure- ments in the (v‘, J’)manifolds. A fast transient recorder and a computer were used to capture and average the fluorescence decays resulting from a number of laser LASER-INDUCED FLUORESCENCE OF IBr pulses, usually 1000 pulses (see Experimental Section).The resulting ffuorescence decay curves gave good fits to a single exponential decay and typical examples are given in fig. 5. Data reduction was carried out using BASIC programs, from batches of results stored on floppy discs. I I 1 0 0.5 1 timelps timelps FIG.5.-Fluorescence decay curves of IBr (B). Typical unsmoothed decay plots are shown for the (2, 12) and the (3,7) ro-vibrational states of IS1Br(B). Note much shorter lifetimes in the u’ = 3 state. (a)I)’= 2, J’ = 12; (b)u‘ = 3,J’ = 7. For several lines, measurements were made over a range of IBr pressures varying between 1 and 5 mTorr. No systematic trend of fluorescence decay rate upon pres- sure could be observed and the lifetimes for the remaining lines were based on measurements taken at one pressure <5 mTorr.Table 4 shows a summary of the measured lifetimes for the ro-vibrational states (2, J’)and (3, J’) of the B states of 181Br. Data for the (3, J’)manifold of 17’Br are also given in table 4. Two major trends are noted from the data. Firstly, the life- time T~ showed a decrease as a function of increasing rotational state, both for v’ = 2 and for v’ = 3. Secondly, the T~ values for v‘ = 3 were all much shorter than those for v’ = 2. The range of r0 values for v’ = 2 of 18’Br was from 290 ns for J’ = 7, M. A. A. CLYNE AND M. C. HEAVEN TABLE4.-sUMMARY OF LIFETIME MEASUREMENTS Zo FOR IBr B3n(o+) no. of transition J' J'(J'+ 1) ~~/10-~s r1/106s-l measurements IelBr P(8) R(7) R(8) R(9) R(11) R(12) R(3 3) 7 8 9 10 12 13 34 56 72 90 110 156 182 1190 2.9 3.5 2.3 2.1 1.6 2.2 0.70 3.5 2.8 4.3 4.7 6.3 4.6 14.3 4 4 4 4 3 2 1 v' = 3 transit ion J' J'(J'+ 1) T~/~O-~s +/lo7 s-l no.of measurements 3 12 7.2 1.4 7 56 6.2 1.6 12 156 5.3 1.9 16 272 5.0 2.0 19 380 4.5 2.2 28 812 2.8 3.6 30 930 3.3 3.1 32 1056 2.8 3.5 10 110 5.2 1.9 11 132 5.2 1.9 14 210 4.1 2.4 16 272 4.4 2.3 22 506 3.4 2.9 25 650 2.9 3.5 down to 70 ns for J' = 34. For v' = 3 of I79Br, rovaried from 72 ns for J' = 3, down to 28 ns for J' = 32. Collisional effects were not investigated in detail; however, no effect upon zo of IBr pressure was found up to 5mTorr. The hard-sphere bimolecular frequency z,, for IBr(B) +IBr(X) collisions was calculated, using dIBr(X) == 5.05 A and dIBr(B) 5.80 A.The value for z,,at 298 K was 3.4 x 10-lo cm3 molecule-' s-l, or 1.09 x lo4 mTorr-l s-l. Therefore, the mean time (1/e) between IBr(X) + IBr(B) collisions, at 5 rnTorr pressure of IBr, is calculated to be about 18 ,us. This magnitude is 40 times greater than the longest lifetime recorded for JBr(B) (see table 4),which is con- sistent with the non-observation of a pressure-dependence for zo in our work. Thus, it can be assumed that the lifetimes presented in table 4are collision-free determina- tions. LASER-INDUCED FLUORESCENCE OF TBr DISCUSSION COMPARISON WITH PREVIOUS LIFETIME MEASUREMENTS Wright and Havey were the only previous workers to have reported a value for the lifetime of the B3rI(O+)state of IBr.They measured the fluorescence decay rate of excited IBr, following excitation with a high-energy flashlamppumped dye laser with a pulse duration of 150ns. Decay curves were recorded following excitation at wavelengths near to the band origins quoted by Selin and Soderb~rg.~ A static fluorescence cell containing IBr was used,8 with pressures estimated to be less than 2 Torr. As no excitation spectra were recorded by Wright and Havey,8 positive identi- fication of the fluorescing species was impossible. Contributions by Iz and Br, fluorescence are probable. Wright and Havey reported zo = 0.53-0.56 ,us for excitation near the band heads of transitions with v’ = 2, 3, 4.There is almost no agreement between these results and those of the present study (table 4). The observed large variations of r0 with v’ and J’ are not revealed by the earlier work, in which broad-band excitation was used.* PREDISSOCIATION OF IBr B3n(0+) Lifetimes of the (3, J’) and 2, J‘) ro-vibrational states of IBr B3n(O+)show strong dependences upon rotational quantum number J’ ;this effect can be interpreted in terms of a natural predissociation. The rotational dependence shows that the predissociation is heterogeneous, i.e., AQ # 0. For a heterogeneous predissociation, the first-order rate constant for predissociation rPdepends upon J’ according to eqn (I>,lS. 16 rp= k,J(J’+l), (1) lf I I I 1 I 0 400 800 J‘(J‘+ 1) FW.6.-Predissociated lifetimesin IBr (B).Plots Of Ti1 againstJ’(J’+ 1) forthe (3, J’)ro-vibrational manifolds of a, 179Br(B)and A, I*’Br (I?). See eqn (11) in the text. M. A. A. CLYNE AND M. C. HEAVEN Thus, the observed decay rate constant z0-l is given by eqn (11), z0-l = z,-' -t kvIJ'(J'+ 1). (11) In the case where predissociation of rotation-free states (J' = 0)is completely for-bidden, the term z, in eqn (11) may be equated to the radiative lifetime zR of the excited state. Eqn (IT) has been found to hold for heterogeneous predissociation in the B311(Ot)states of 12,l1 Br29 and C12.17 -~Fig. 6 shows plots of T~ against J'(J'+ 1) for the v' = 3 states of IS1Br(B) and of 179Br(B). Satisfactory linear correlations for both v' = 2 and v' = 3 were obtained, with the following values for z,/ns and kVr/s-l: v' = 2 of IslBr : z, = 441, k,, = 1.1x lo4; v' = 3 of IS1Br : z, = 70, k,.= 2.1 x lo4 ; V' = 3 of 179Br : z, = 62, k,. = 2.8 x lo4. The values z, are much shorter than the estimated magnitude of zR (see below). Also, z, for v' = 2 is 441 ns, whilst z, for v' = 3 of IS1Br is 70 ns. The results sug- gest that there is a strong rotation-free component of the predissociation in IBr B311(O+). The decrease in z, between v' = 2 and v' = 3, involving an energy in- crease of 124 cm-l, indicates that the classical crossing point with the B state is being approached. This crossing point between the B31T(O+) state and the repulsive Of state is believed to be located near the v' = 5 level of the B state.The failure in our work to observe fluorescence from the v' = 4 level is consistent with this description and suggests z, < 5 ns for v' = 4. The slightly lower values for z,-l and k,, of v' = 3 of compared with those of the same level of 179Br, may be significant. The absolute energy of v' = 3 of the lighter isotopic species 179Br is almost 3 cm-l greater than that of I 81Br; therefore the vibrational level ZI' = 3 is slightly closer in energy to the curve-crossing in the case of the E79Br species. Thus, ~ml(I~~Br) > T;'(IS1Br). The nature of the predissociation in the B3n(O+)state involves both rotationally- dependent and rotation-free terms, according to the present results. Arguing by analogy with information that is available for the other halogens and interhalogens, it is probable that an interaction between the B3n(O+)state and a lIT(1) unbound state is responsible for the observed predissociation.This interaction, with a lII(1) re- pulsive state correlating with two ground-state atoms, is well established for the B311(O+)states of I2l1, l6 and Br2.9 Olson and Innes l8 suggested that the lII(1) state is responsible for the heterogeneous predissociation in ICl(B), below the point of intersection with the repulsive Of state. Firm evidence that ln(1) crosses B311(O+)at lower energies than the Of state (in ICl) was provided by Bondybey and Brus,19 who studied the relaxation dynamics of matrix-isolated IC1. For C12, homogeneous radiationless processes involving the lII(1,) and the B3IT(O;) states have been suggested by Clyne and McDermid.l' They proposed that interaction of a homogeneous nature may occur in C12 because, either the 'II(1,) state is mixed with an 0,-type state; or the B state acquires partial 1,-character by mixing, for instance, with the A311(lu) state.I7 In summary, if it is assumed that interaction of the B311(O+)state of IBr occurs with the 'II(1) state, there are two possible ways in which the observed predissociation 0';viahomogeneously,andlIT(l),via(i) Heterogeneously, can occur.or (ii) combined heterogeneous and homogeneous predissociation via lI(1). Further in- formation is required in order to determine unequivocally the character of the pre- dissociating states of 1Br.LASER-INDUCED FLUORESCENCE OF IBr RADIATIVE LIFETIME ZR OF IBr(B-X) Sufficient information is available on the electric dipole moments (ReI2for the B-X transitions of the halogens and interhalogens, for it to be possible to predict a value of IRe12for IBr, within a factor of two uncertainty. Clyne and McDermid20 have collected the current values of IReI2for the B-X transitions [see table 3 of ref. (20)]. Excluding Cl,, the variations in IReI2 through the series of halogens and interhalogens encompass only a 28-fold range of values.20 Using these data for lRe12, i.e., a value of 1.0 D2 for and a value of 0.4 D2for BT,,~ a value of 0.7 D2 may be estimated for IBr. The relation between IReI2and the radiative lifetime zRof a transition is given by eqn (IIIa) :22 (IIIa) where qut,u” is the Franck-Condon factor for the transition d-v”.Assuming that 1ReI2 varies insignificantly with r-centroid for the range of the most intense transitions, eqn (IIIa) can be recast in the simpler form of eqn (IIIb) : zR1 = (64n4/3h)IR,12(v’)3; (1116) in eqn (IIIb), v’ is defined by (93 = c v~t,v“qv’,u”) 1)” where vVr,utt is the wavenumber of the band origin v’-v‘’. A value for V may be estimated by evaluating the summation for all U” states. Previous qvt,vIt calculations l3 did not extend reliably above U” = 7, but the present data (table 2) are based on the new ground-state spectroscopic data of Weinstock and Preston for v” < 19. Because of the small energy separations between consecutive 21‘’ levels in IBr XIX+,a large number of terms (v” 30) are needed in the summation to find v’, in order to avoid significant truncation errors.Summation up to v” = 50 involves small extrapolation errors and gives 5 = 11 650 cm-1 both for v‘ = 2 and for v’ = 3, which, however, should be accurate to +lo %. Substitution into eqn (IIIb) of the values IReI2 = 0.7 D2and v’ = 11 650 cm-l then yields a value of 3.9 ps for the radiative lifetime of IBr B3rI(O+). This estimate ap- plies to emission from the states v’ = 2, 3 and should be reliable to within a factor of two. Comparison of the estimated value zR = 3.9 ps with z, = 0.44 ps (for v‘ = 2) = 0.07~~(for v’ = 3) confirms that the measured rotation-free lifetimes of IBr(B) contain major components from predissociation, as has been argued above.It will be interesting to discover whether the lowest vibrational levels (v‘ = 0, 1) of IBr(B) also have lifetimes that are strongly affected by predissociation. All the levels of the B-state manifold of IBr have energies greater than that of ground-state 12P++Br2P3 atoms. This is also true for all levels, except v’ = 0, of the B3rI(O;) state of Br,. However, the lowest-energy state for which measurements at present are available, namely v’ = 3 of Br2(B), shows only a weak predissociation and z, is close to 7, in this case.9* 23 The case of the B3rf(O+)state of ICl also is interesting, since the level v’ = 0 is stable to dissociation, whilst the higher levels U’ = 1, 2 axe located above the dissociation limit for 12P++C12P+ atoms.The present work on IBr calls into question earlier results on ICl(B),24*2s in which no strong dependence of 70 upon v’ or J’ was found. Clyne and McDermid 24 reported zo = (0.52$-7, and M. A. A. CLYNE AND M. C. HEAVEN 65 E;::) ps for several rotational states of II’= 1, 2, based on fluorescence decay measure- ments in the Torr pressure range of LCl. On the other hand, McDonald and Miller 25 reported the higher value zo = (4.4k0.2)ps, using lower rotational resolution of the IC1 bands. They 25 worked in the mTorr pressure range and thus their extrapolation to zero pressure should be more accurate than that of Clyne and M~Dermid.~~ Further studies of the lifetime of ICl(B), as a function of II‘and J’, clearly are required.Both high spectral resolution and low pressure should be employed, in order to verify whether or not zo depends upon v’ and J’in a manner similar to that reported here for the B state of IBr. ROTATIONAL DISTRIBUTION OF J’-STATES IN IBr(B) As has been indicated above, the rotational intensity distribution of fluorescence, which was observed in the laser excitation spectrum of IBr(B-X), was strongly non- Boltzmann. Although the Boltzmann distribution in the ground state has a maximum near J” = 42, the peak intensity was seen near J” = 25 in bands with v’ = 2 and 3 (see fig. 4). Neglecting the small effect of rotation upon the Franck-Condon factors, the deviation of the observed fluorescence intensity from that predicted by the Boltzmann distribution is given by the fraction r9, fD = ZOIZR. This analysis assumes no collisional effects ; then @ is equal to the quantum yield of fluorescence out of the excited state J’.According to the data of table 4 and the estimated value ‘tR = 3.9 ps, r9 decreases in the state II’ = 2 of PIBr from @ = 0.11 at J’ = 0, down to @ = 0.012 at J‘ = 42. The range of values of r9 in the state v’ = 3 is calculated to be from 0.010 to 0.005 over the same range of J’. Thus, the rapid decrease in r9 with increasing J’ gives fluorescence intensities which maximise at rotational quantum numbers considerably below the Boltzmann maximum. A similar but more extreme situation has been seen in the laser-induced fluorescence of Cl,, where maximum intensity is observed from rotational states with J’ = 1 to 3.l’ In conclusion, the requirement for exciting resolved ro-vibrational states with a narrow-band laser has been demonstrated clearly in the case of lifetime determinations of IBr(B).Both 0’ and J’ affect the lifetimes and misleading results will be obtained if more than one quantum state is excited simultaneously. We thank R. Chaplin for assistance with the construction of the dye laser, and L. Goldberg of the Naval Research Laboratory and P. Sarkies of JK Lasers for helpful advice. Support of this work by the Royal Society, the S.R.C. and the U.S.Air Force Office of Scientific Research (Grant AFOSR-75-2843) is gratefully acknowledged. W.G. Brown, Phys. Rev., 1932,42,355. L. E. Selin, Arkiv Fysik, 1962,21,479 ; 1962,21,529. L. E. Selin and B. Soderborg, Arkiv Fysik,1962, 21, 515. M. S. Child, Mol. Phys., 1976,32, 1495. M. S. Child and R. B. Bernstein, J. Chem. Phys., 1973,59, 5916. ti E. M. Weinstock, J. Mol. Spectroscopy, 1976,61,395.’ E. M. Weinstock and A. Preston, J. Mol. Spectroscopy, 1978,70, 188. J. J. Wright and M. D. Havey, J. Chem. Phys., 1978,68,864. M. A. A. Clyne and M. C. Heaven, J.C.S. Faraday II,1978,74,1992. lo M. C. Heaven, Ph.D. Thesis (Queen Mary College, University of London, 1979). l1 M. A. A. Clyne and I. S. McDermid, J.C.S. Faraduy 11, 1978,74, 1376. l2 M. Broyer, J. Vigue and J. C. Lehmann,J. Chem. Phys., 1975,63,5428. II-3 LASER-INDUCED FLUORESCENCE OF IBr l3 M.A. A. Clyne and I. S. McDermid, J.C.S. Faraday II, 1976,72,2242. l4 J. A.Coxon, J. Quant. Spectroscopy Radhtive Transfer, 1971,11,443. l5 R. Kronig, 2.Phys., 1928,50,347. l6 J. Tellinghuisen, J. Chem. Phys., 1972,57, 2397. l7 M.A.A. Clyne and I. S. McDermid, J.C.S. Faraday II,1979,75, 1677. C. D.Olsen and K. K. Innes, J. Chem. Phys., 1976,64,2405. l9 V. E.Bondybey and L. E. Brus, J. Chem.Phys., 1975,62,620;J. Chem.Phys., 1976,64,3730. 2o M. A.A. Clyne and I. S. McDermid, J.C.S. Fwahy 11, 1979,75,280. 21 A.Chutjian and T. C. James, J. Chem.Phys., 1969,51,1242. 22 F.Zaraga, N. S. Nogar and C. B. Moore, J. Mol. Spectroscopy, 1976,63,564. 23 M. A.A. Clyne and M. C. Heaven, J.C.S. Faraday 11, to be submitted. 24 M. A. A. Clyne and I. S. McDermid, J.C.S. Faraday II, 1977,73, 1094. 25 J. R.McDonald and R. G. Miller, unpublished data. (PAPER 9/381)

ISSN:0300-9238    

DOI:10.1039/F29807600049

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

J.C.S. Faraday II, 1980,76,67-81 Non-local Screening in a Polar Solvent BY KAREL HOLD* AND ALEXEYA. KORNYSHEV? J. Heyrovsky Institute of Physical Chemistry and Electrochemistry of the Czechoslovak Academy of Sciences, JilskiL 16, Prague 1, Czechoslovakia Received 19th March, 1979 Non-monotonicfunctions of the spatial correlation of the polarization fluctuations of the medium are proposed. The non-monotonic character of these correlation functions leads to the non-monotonic behaviour of the screening factor for the field of a point charge. Interpretations as well as raisons d’&treof the proposed models are discussed. The concept of non-local screening expressed in terms of dielectric formalism with a spatial dispersion 1* is now a powerful tool for the description of phenomena due to electric interaction on the interatomic scale (both in the bulk and near interfaces of condensed media).3 The general formalism was designed to express the relevant properties through the dielectric function of the system E~~(w,k, k’).In this way expressions were found, e.g., for self energy of electron gas in infinite and semi-infinite solid state plasmas, image 6*’and adhesion,8 polaron ground state,9 critical temperature of transition into superconductive state in the bulk and interfacial sys-tem~,~the kinetic parameters characterizing the reorganization of polar media in the course of phonon assisted charge transfer reactions.1o* l1 The models for permit- tivity were employed to obtain both qualitative and quantitative results.In static problems, the results are frequently expressed, due to dispersion relations, through the static permittivity e(u, = 0, k, k’), so that for a homogeneous system it is sufficient to know s(0,k) = E(k). The static dielectric function e(k) contains infor- mation on the many-body properties (the “ structure ”) of the medium. It has been calculated approximately for the simplest systems. These are, for example, the Lindhard expression for an electron gas in the Hartree approximation and subse- quent generalizations of the random phase appr~ximation.~ Some results have been obtained for dielectrics on the basis of band structure theory.12 The purpose of the investigation of these much more complicated systems was usually not to find the whole expression from first principles, but to assume that some quantities were known (such as energy gaps, electronic wave functions, etc.) and so to outline the collective phenomena, leading to the non-local screening effects.The results thus obtained were either too complicated or oversimplified. Accordingly it was necessary to propose simple analytical interpolation formulae which are adapted to established limiting behaviour 3-1 or numerical results. The substitution of analytical formulae for E(k)in the results of dielectric formalism enables one to describe the effect under study through the parameters involved in e(k),which reflect the collective properties of the medium. In this manner interesting sequences were obtained for interfaces [for review see, e.g., ref.(17)-(lg)], where the results are determined not by the gradual change of the screening in one component, but by the “ competition ” between the screening properties of the media in contact. t On leave from the Institute of Electrochemistry of the Academy of Sciences of the U.S.S.R., Moscow, U.S.S.R. 67 NON-LOCAL SCREENING IN A POLAR SOLVENT The effects of spatial dispersion, resulting in the non-local screening of ionic field should be important in a set of the so called structured polar solvents, such as water or the alcohols. In these liquids hydrogen bonding chains are supposed to provide significant spatial correlations in the orientational fluctuations of the dipole moments of molec~les.~~-~~ This correlation should be stronger than in simple polar fluids with purely electrostatic dipole-dipole interactions.The range of correlation, A, may approach the characteristic range of the hydrogen bonding chains (different esti- mates lead to values of the order 10A).25*26 This “long-range ” correlation should ultimately lead to the non-locality of screening and to the dependence of E upon k at least at k w A-l. The function E(k)cannot be analytically calculated at present from first principles for a polar liquid. At the same time, knowledge of an analytical (“semi- phenomenological ”) expression is highly desirable, if such a function is intended to be utilized in the analysis of different solvent determined phenomena (thermodynamics of solvation, statistical mechanics of ionic solutions, double layer capacitance, charge transfer transition probability, solvated electron energy spectrum, etc.)In order to analyse E(k), it is convenient to start with a relation, based on an approximate fluctuation-dissipation theorem (AFDT), obtained in ref.(27). We reproduce here a special case of this AFDT, valid for classical degrees of freedom (with the characteristic frequencies o -c T/h). It gives an expression for E(k) through the correlation function flUj?(R) = <I3,(R)~j?(O)>* (1) This function describes the spatial correlation of fluctuations of the polarization of the medium ysociated with the excitation of classical degrees of freedom. Thus, in polar liquids, P incorporates only the contribution due to hindered dipole rotations (the so-called orientation Debye polarization). AFDT relates rI(k) = -dR IIap(R) exp (ik R) = 1: dR 4nR2{ IIll(R) sin kR +2[IIL(R) -IIlI(R)](r- sin kR where IIll(l?) and are the longitudinal and transverse components of the tensor IIaBin R-space, to E(k) = e(o = 0,k) and E*(k) = E(W 21 w*, k).The latter is the permittivity at the frequelcy co N ow,which is the upper bound for the frequencies giving a contri- bution to P. The relationship is where T is the temperature in energetic units. [Strictly speaking, the derivation of eqn (4) requires the modes contributing to P^ to be separated from the higher fre- quency spectrum by the band with low oscillator strengths.Namely, that ImE(o 21 o,,k) Q ReE(W N a*,k) = ReE*(k) (a weak function of co at co N co,)]. K. HOLUB AND A. A. KORNYSHEV The low-frequency orientational modes have the largest correlation length. Therefore, bearing in mind that we shall deal with k not larger than inverse interatomic separation we may put &*(a)N E* = const and write the direct expression for E(k): where E = E(k = 0), the " macroscopic " dielectric constant. In this paper it will be sufficient to take E(k) given by eqn (5) since large values of k, at which E*(k)starts to depend upon k, would not give a significant contribution to the resulting quantities. However, when this is not so, a more general expression which also involves the dispersion of higher frequency modes 27 is required.Sometimes it is the dispersion of these modes which plays the main role in the phen~menon.~~ Now the problem of the form of E(k) is reduced to the study of the correlation function IT(k). However, the results in screening theory can be expressed directly through II(k) or ITa@). Then using our knowledge of the limiting behaviour of II(R)we can judge the limiting properties of the quantity under study. The second advantage of this phenomenological approach is that we can calculate the quantity expressed through IIaB(R)if the model approximation or computer simulation is available for this function. Finally, the problem is regarded as solved if IIap(R)can be obtained from an independent experiment. Unfortunately, no reliable procedure has been yet proposed for measuring this function in a polar liquid?* It would be helpful to reveal some general properties of n(R)to restrict the possible variations of approximating functions. Some of them were formulated in ref.(27). In this paper we shall try to develop some further detailed concepts. Moreover, we shall use some of the appropriate approximations (satisfying the general properties) to show the effect of the "details " of these approximations on the screen- ing properties of the solvent. We note that the importance of more detailed structure concepts for screening phenomena in polar liquids has been already empha~ized.~ In this communication we shall study only the screening of a field of a point charge in a uniform solvent.Also we shall discuss the field of a single ion in the solvent with account taken of its final size effect (see Appendix 1). The study of more thermo- dynamic quantities, interfacial characteristics, kinetic parameters, etc., will be given in later publications. PROPERTIES OF THE SPATIAL CORRELATION FUNCTION n(R) POSSIBLE ANALYTICAL APPROXIMATIONS In ref. (27), a representation of nIl(R)and IIL(R) was proposed which takes account only of one necessary requirement : that the correlator should degenerate into a S-function in the limit of an infinitely small correlation range. Therefore, it was concluded 27 that II must be a generalized b-like function of the parameter of non-locality, A, of the type -4(R/A)/A3, where 4 + 1with R/A 4 1 and 4 + 0 with RIA 1.Results were then formulated as functions of 4, whereby this limiting behaviour (with respect to one parameter, A) led directly to the relevant asymptotic results. To obtain the analytical formulae, approximations satisfying the mentioned properties were proposed :4(x) = e-x, 4(x) = e-x2,4(x) = O(x-l), etc. They were applied to the analysis of ionic s~lvation,~~ thermodynamicsinterionic intera~tion,~~ of ionic solution^,^ solvent determined kinetic parameters of charge transfer, O solute dipole-dipole intera~tion,~~ etc. In addition to the above-mentioned one parameter S-like representation of the NON-LOCAL SCREENING IN A POLAR SOLVENT correlation function another assumption was used there, namely that II does not con- tain the separate &function contribution.A discussion of this question is given in Appendix 2. We shall consider a two-parameter representation of the &like model for cor- relation functions IIll(R) and ITL@). First, we shall perform the analysis formally as the study of a more general type of &like functions admissible for the approxi- mation of IIII(R)and Ill@). Later we shall discuss the reasons for the choice made and the results which arise. One may propose the same type of analytical expressions for both II"(R)and II'(R) components of the tensor attributing all the differences in these functions only to the values of their parameters. Even this may not be true, since the projections of polarization fluctuations at two different points on the axis passing through these points and the projections onto the plane normal to this axis are correlated in a different manner. This concerns pri- marily the correlation at small distances.This effect would influence the second item in the integrand of eqn (2) and would lead to rather cumbersome expressions for II(k). Since our aim is to reveal the effect of the second parameter, we shall avoid this complication by putting nil(@= W(R)= II(R). (This assumption is quite usual 33 and not too severe for non-magnetic liquids 27.) Then eqn (2) is reduced to sin kRdR4nR211(R)-kR and rIo II(k = 0) = 1: dR4nR211(R). We shall consider three &like approximations for n[(R): In the limit of Q = 0 these expressions are reduced to the one-parameter "expo- nen ti aI " approximati on.ANALYTICAL FORMULAE FOR THIS STATIC DIELECTRIC FUNCTION Following eqn (5), to determine E(k) it is sufficient to calcuIatef(k) = n(k)/II,.For each of the approximations (7)-(9) we have, respectively, K. HOLUB AND A. A. KORNYSHEV 1+s2(2) f(k) = F~(s,X) -arc tan 2s2x 3+ 2s2-S4+2(s2+ 1)x2-x4 [l +(x-s)~]~[~+(x+s)~]~ where x = kA, s = QA. When s 0 all these expressions are reduced to f(k) = F~(X)= (1+~~)-~, (13) the same result as the exponential appr~ximation.~’ Fl, F2 and F3 possess different analytical properties from Fo. The latter have only two second-order poles on the imaginary axis at 2 = +i. Fl has four simple poles in the complex plane : Z = +i+s.F3 has second-order poles in all the points mentioned above. The singularities of Fzdepend upon the value of the parameter s. SCREENING OF THE FIELD OF A POINT CHARGE The potential due to apoint charge in a uniform medium with spatially dispersive permittivity e(k)is a sinkr 1dk --kr E(k)’ (14) If the system does not contain free charge carriers and E(k + 0) = 8 = const (the case of an insulator)? then it is convenient to rewrite eqn (14) in the form outlining thereby the screening factor The substitution of eqn (5) into eqn (16) gives S(r) = 1+(t-l);J0 “dk [l-f(k)] sin kr; t=&I&*.2 Insertingf(k) for each model [see, e.g., eqn (10)-(1211 provides the concrete analytical result for the screening factor. Some general properties of S(r) can be predicted simply on the basis of the analytical properties of f(k).Since f(k = 0) = 1 and f(k + GO) + 0 [see eqn (16)], S(r) varies from at r = 0 to 1 at r + m. The way in which it varies from to 1 depends upon the behaviour off(k). Indeed, since limk-,,[l -f(k)]= 0, the integral in eqn (17) decreases as r + GO. If [l -f(k)] has poles only on the imaginary axis (k* = iqJ, it decreases exponentially { =exp[-r min(~~)]}. If the poles are also at complex values of k, the integral in eqn (17) will be an oscil- lating function of r. Oscillations may also arise as a consequence of more complicated ~ingularities.~~Thus, monotonic behaviour of S(r) follows only with rather severe restrictions on f(k). Eqn (17) is not convenient for calculation of S(r)if one starts from the expression NON-LOCAL SCREENING IN A POLAR SOLVENT for II(R).Substituting eqn (6) into eqn (17) and performing the integration over k, we find a direct expression for S(r) through n(R): S(r) = l+(c-l)j 00 dR4nR2n*)(1-i). r n0 Substitution of II(R) in the form of eqn (7), (8) or (9) into eqn (18) gives for each model, respectively : sin 2Qr sin2Qr(2) S(r) = l+(c-l)e-rlA {I+-+--2QA 2Q2A2 (3) S(r) = l+(e-l)e-r’A [l+QA 3-~2~2-1 x (1+QA) l+-+ [3 -Q2A2+(1+Q2A2)5]QA cos Qr}}. (21)A L In all three models we obtained non-monotonic behaviour of the screening factor. Oscillations in eqn (19)-(2 1) are not surprising since the corresponding dielectric -15 -10 -5n \jtl 0 2 34 5 rlA FIG.1.-Non-local screening factors, corresponding1to different models for the correlation of polar-ization fluctuations in space, model 1 [eqn (711.S(R) calculated via eqn (19). QA = (a) 0.5, (6) 1 and (c) 3. K. HOLUB AND A. A. KORNYSHEV I -15 $=lS/ -10 h & -5 h -0 FIG. AS AS fig. 1. Model 2 [eqn (811. S(R) calculated via eqn (20). QA = (a) 0.5, (b) 1 and (4 3. 3 1 I I 1 I 5 10 2 5h &t3 1 0 -5 I I I I I 1 23 45 riA FIG.3.-As fig. 1. Model 3 [eqn (911. S(R) calculated via eqn (21). QA = (a) 0.5, (b) 1 and (c) 3. NON-LOCAL SCREENING IN A POLAR SOLVENT functions l/~(k)had poles at complex values of k. If Q = 0, the screening factors eqn (1 9)-(21) degenerate into monotonic functions S(r) = 1 +(<-1) exp(-r/A)[l +r/(2A)] (22) obtained previously for the simple exponential 31 Plots of the screening factors (19)-(22) are shown in fig. 1-3.The potential in the form (15) can be rewritten as 4(r) = q/[~(r)r]where E(Y) = c/S(r) is an “effective dielectric constant ” which varies with distance. According to results presented above for S(r), e(R) varies from E* (21 5, for water 23) at small distances to E (-80, for water) at large distances from the charge. In the case of the simple exponential approximation, E(Y) = ~(1+(<-1)exp(-r/A)[l+r/(2A)])--i, the variation of ~(r)is monotonic. Other screening factors, like eqn (19)-(21), lead to non-monotonic behaviour of ~(r).This concept of spatially-varying local permit- tivity has been used in numerous publications on electrolyte theory.”~ 36 This was done either to account for dielectric saturation phenomena or in a search for a more appropriate description of solvent structure This approach was proposed as an alternative to the primitive model of a structureless solvent (E = const). Monotonic and non-monotonic models for ~(r)were proposed without any foun- dation.Thus a proper justification for speculations on spatially varying E is, in some sense, given by the non-local theory with spatial dispersion. This does not mean, however, that the procedure of using fixed ~(r)can easily replace the present treatment (with account taken of non-local response) in the calculation of different quantities.If the results obtained for each quantity within the rigorous non-local theory are rewritten with the help of some effective functions ~(r),these functions would have a different form in each case. For instance, “effective ~(r)” for the electrostatic interaction energy of ions of finite size differs from ~(r)for the screened potential of an isolated ion. Thus the construction of a theory based on a fixed dependence ~(r) may lead, sometimes, to wrong results. DISCUSSION The dielectric functions eqn (5) and (10)-(12) and the screening factors eqn (19)-(2l), obtained formally from different &like representations of the correlation function II(R)[eqn (7)-(9)], reflect more detailed short-range structure in the solvent dielectric response.The scale of this structure, Q-l, is of the order of the molecular size. The results for k x Q are less justified from the theoretical point of view and are usually considered as a sort of extrapolation (intended to describe experiment). However, in the results for the screening factor, the effect of Q # 0 is manifest not only for Y w Q-l, but also at larger distances, of the order of A [cf. ref. (13) and (34)], where the dielectric response theory has a solid foundation. Different &like approximations may correspond to different structural restrictions on the dipole orientation correlation in a polar liquid. The first model might cor- respond to the most strict orientational structure. The second model has periodical dips in correlation.These dips may be due to the presence of intersites with quasi- free molecules (weakly associated with the skeleton) which are quasi-periodically distributed inside the network. The third model may be thought to reflect the quasi- periodical structure in the distribution of dipole centres with the decay characteristic for liquid systems and also with the decay arising from the decrease of angular corre- lations with distance. K. HOLUB AND A. A. KORNYSHEV 75 The differences which are demonstrated by these models in screening can be fol- lowed from fig. 1-3. So, the details of the '' correlation structure "play an important role in the absolute value and arrangement of the average electrostatic potential around the charged impurity in a polar solvent.The model examples considered show that this arrangement may result in a periodical alternation of the sign of the electric field. The depth of the observed minima in the potential 4(r) may be esti- mated for specified values of (, A and Q. For instance, in the case of Q N 2n/l(I is the molecular size) and A > 21, model 1 gives for the first minimum: &,in 5 (T/e)(l&/Z), where LB= e2/(cT)(the Bjerrum length). In water, if > 3 it gives #min 6 10TIe. In other models the minima are not so well defined, but their depth can exceed the thermal energy for sufficiently large <. The present study was motivated by experimental verification of the predictions of the spatial dispersion theory in polar liquids. After an encouraging application of non-local theory to the thermodynamics of ionic hydration 23 it seemed that the representation of the correlation function with one parameter of non-locality is suf- ficient to explain the data.Later it became clear that for acceptable values of para- meters (&* N 5, A = 10) the absolute value of the interionic potential in water turns out to be too large. This leads to an overestimation of the interaction energy in the statistical theory of aqueous electrolyte solutions, which makes the explanation of the data on activity coefficients rather diflticult. Such a large monotonic increase in repulsion between ions of the same sign leads also to discrepancies in the theory of electron transfer reactions.For instance, the rate constant k in the simple outer- sphere electron transfer reaction MnQ, +MnQi-+ MnOg-+MnQi in water as solvent is k x exp(-W(r*)+Ea(r*)]/T}.io In the case of a very dilute solution, W(r,) is the energy of interaction of reactants in the transition state, Ea(r*)is the activation energy due to the reorganization of the solvent, r* is the interionic sep- aration in the transition configuration. If one parameter correlation functions [see eqn (13)] and E* N 5, A = 10, are used in estimates of W(r) and Ea(r) then the energy of electrostatic repulsion W(r)is considerably greater than the energy given by Coulomb's law, but the activation energy is smaller than E, given by the Pekar- Marcuse formula lo (in which spatial dispersion is neglected). Fitting of the ex- ponent to data on the slope of In k against 1/T gives Y, = 11 A.27 However, this distance is in contradiction to the fitting of the pre-exponential factor: at such a distance the overlap of electronic wave functions is so small that the total rate con- stant is several orders of magnitude lower than that Studies of some other outer sphere reactions have also revealed this di~crepancy.~' Furthermore, ionic pair formation is much better described within the macroscopic Bjerrurn description 39 than using the non-local theory based on spectral function (1 3).38 At the same time the results of non-local theory in the treatment of ionic solvation were much better than those of the Born theory, which operates with macroscopic E.The resolution of these paradoxes now seems to be clear. All the listed dis- crepancies were associated with an overestimate of the ionic field in a rather broad region around the ion. Within a single parameter representation of the correlator II(R),the whole Debye polarization is regarded as one mode with a single correlation range A. Since the magnitude of A is rather large, the contribution of the whole Debye polarization to the polarizability of the system is seriously diminished. Practically, only the higher frequency modes (with small correlation length) are able to screen the ionic field within the radius <A. Presumably, the Debye polarization cannot be considered as one mode, but as a set of modes with different correla- tion range.In ref. (40) the Debye polarization was assumed to consist of a low frequency mode with a large correlation range and higher frequency modes with NON-LOCAL SCREENING IN A POLAR SOLVENT negligible correlation range. This procedure immediately decreases 5(from previously supposed values of 16 to, maybe, 3, in water) in eqn (17), so that the ampli- tude of the non-local effect is reduced.40 In this paper we consider an alternative approach :the whole Debye polarization is described by total P,but the correlation <P(r)P(O))was assumed to have a more complicated form reflecting the " structure " in P. In this manner we obtain new flexible analytical expressions for E(k) and the screening factor which may be capable of explaining the experiments even with large values of 5 and A.This modification would not greatly affect the results on solvation energies.23 The contribution of orientational polarization to the total electrostatic solvation energy does not exceed 20 % if all the effects of spatial dispersion are neglected. Taking account of spatial dispersion it may be reduced to 5-10 %.23 Thus, the final result is not very sensitive to the models proposed to describe correlations in Debye polarization. The agreement 23 of the theory with experiment was associated with due account of the spatial dispersion of the higher frequency modes [calculated on the basis of more complicated formulae than eqn (5)]. The correlation ranges for these modes are significantly smaller than A.23 Therefore, the use of one parameter cor- relation functions for each mode was sufficient to obtain reasonable results.CONCLUSION This account of more detailed structure concepts in the spatial correlations of polarization fluctuations may be capable of resolving contradictions arising in the applications of non-local theory when such " details " are neglected. The non- monotonic potentials discussed in this paper possess sufficient flexibility to fit the experimental data. Having established the importance of the "fine structure " in the spatial corre- lations, we conclude that no serious progress can be made by the theory without accurate experimental data on E(k). The main effort should be given to the develop- ment of the method of measuring this function for polar liquids, If these data can be obtained, the numerical values of E(k) can be substituted into various expressions containing this function.At the same time, with the help of AFDT(5) (or its modifi- cations 27) these data will give extremely valuable information on the dynamic structure of polar liquids. We thank Drs. V. M. Berdnicov and M. A. Vorotyntsev for stimulating discussions preceding the accomplishment of this work. We especially thank Prof. R. R. Dogonadze who has drawn our attention to this problem. APPENDIX 1 SCREENING OF A SINGLE ION IN A POLAR SOLVENT: EFFECT OF THE FINITE SIZE OF THE ION The general expression for the field of a unit point charge located at the point rj is It provides the result for the potential produced by the distribution of external charges.If this distribution is rigid and characterized by the charge density p(rj), K. HOLUB AND A. A. KORNYSHEV where p(k) 3 1dr, exp (-ik rj)p(rj). (1.3) We consider a spherical charge distribution p(r) = p(lr1) with a centre at r = 0. Then P(k) and p(k) = 4nSOD dr r2 sin -(kr) 0 kr In the case of a point charge p(r) = 6(r)4/(4nr2), p(k) = q and eqn (1.4) gives eqn (14). Eqn (1.4) and (1.5) can be used to estimate the effect of the finite size of the ion on the field produced by the ion in a polar solvent. The estimate neglects the '' break " in correlation of the solvent polarization due to the finiteness of the ion size.41*42 Account is taken here only of the spatial distribution of external charge.The analysis involving both effects leads to more complicated expressions 42 which we shall not discuss here. The Born model of an p(r) = 6(r-a)/(4na2)(a is the effective ionic radius), gives (1 -6) [cf.ref. (30)]. Substituting eqn (5) and (6) into eqn (1.6) and performing the integration over k,we find Sa(r) = S(r)+ASa(r) (1.8) where S(r) is the screening factor for a point charge;18 AS,(r) is the correction to the screening factor due to the finiteness of ionic radius : AS,(r) = (t-l){f+' dR 4nR n(R)(r-a-R)2-1r+a dR 4nR nx)(R -r) -r-a n, 4a r n0 The estimate of the correction due to finite ion radius can be made via this formula by the substitution of the approximation for II(R), used in the calculation of S(r).Models (7) and (9) provide the result in analytical form. We shall not present these cumbersome expressions here. Expanding eqn (1.9) as a Taylor series as powers of a, we find (1.10) The criterion of validity of this formula may be written as (1.11) For instance, if l-I M exp( -r/A),the criterion is NO N-LOCAL SCREENING IN A POLAR SOLVENT 1 2 3 4 5 rlA FIG.4.-The effect of finite ion size on the screening factor for different models of the correlation of polarization fluctuations in space. ASa(r) calculated by means of the approximate formula (l.lO),model 1 Ieqn (7)]. a/A = (a)0.2 (b)0.5 and (c) 1. FIG.5.-As fig. 4. Model 2 [eqn (8)]. a/A = (a)0.2, (6) 0.5 and (c) 1. K.HOLUB AND A. A. KORNYSHEV ie., when r M A, a2 4 1OrA is required, and when Y % A, a2 -4 20A2. Therefore, an approximate formula (1.10) should work quite well for r = 2a (and A = 2a). The results for the screening factor (1.8) calculated via eqn (18) and (1.10) with the help of the approximations (7)-(9) are plotted in fig. 4-6. APPENDIX 2 It has been assumed that II(k -+ co) = 0, i.e., II(R) does not contain any per- manent &function contribution. The assumption TI[@ + m) = const # 0 can be shown to lead to the same form of the function ~(k).Let II(k + 00) = const. Then according to eqn (5) where IT&) = n(k)-const ; II,(k -+ 00) = 0. This equation can be written in the form wherefo(k) = II,(k)/lI,(O) and const NON-LOCAL SCREENING IN A POLAR SOLVENT We see, therefore, that without loss of generality we can assume n(k-+ 00) = 0 or f(k + 00) = 0.The only difference is then the interpretation of the value of E,. If n,(O) > 0, const > 0, E > E,, then E* < ZJI < E. D. Pines, Elementary Excitations in Solids (Benjamin, New York, 1963).W. Harrison, Solid State Theory (McGraw-Hill, New York, 1970).The Problem of High Temperature Superconductivity, ed. V. L. Ginzburg and D. A. Kirzhnits (Nauka Pbl., GIFML, Moscow, 1977, in Russian).K. S. Singwi, in Linear and Nonlinear Electron Transport in Solids, ed. J. T.Devreese and V. E. Van Doren, Advanced Study Institute, Ser. B Physics (Plenum Press, New York, 1976).me Problem of High Temperature Superconductivity, ed.V. L. Ginzburg and D. A. Kirzhnits (Nauka Pbl., GIFML, Moscow, 1977, in Russian).4K. S. Singwi, in Linear and Nonlinear Electron Transport in Solidr, ed. J. T. Devreese and V. E. Van Doren, Advanced Study Institute, Ser. B Physics (Plenum Press, New York, 1976).J. Heinrichs, Sol. State Comm.,1973,13,1595,1599. J. Heinrichs, Phys. Rev., 1973, B8,1346. A. A. Kornyshev, A. I. Rubinshtein and M. A. Vorotyntsev, Phys. Stat. Solidi (b)1977,84,125; K. Holub, A. A. Kornyshev, A. I. Rubinshtein and M. A. Vorotyntsev, Surface Sci., to be submitted. A. A. Abricosov, L. P. Gorkov and I. E. Dzyaloshinskii, Methods of Quantum Field Theory in Statistical Physics (GIFML, Moscow, 1962, in Russian).J. Devreese, R. Evrard and E. Kartheuser, in Elementary Excitatwns in Solidr, Molecules and Atoms, ed.J. T. Devreese, A. B.Kunz and T. C. Collins, (Plenum Press, London, 1974), p. 131. lo R. R. Dogonadze and A. M. Kuznetsov, Kinetics of Chemical Reactions in Polar Solvents, VINITI, Ser. Physica 1 Chemistry, Kinetics (VINITI, MOSCOW, 1973), vol. 2. l1 R. R. Dogonadze and A. M. Kuznetsov, Progr. Surface Sci. 1975,6,1. I2 H. Ehrenreich and M. H. Cohen, Phys. Rev., 1959,115,786; P. K. W. Vinsome and M. Jaros, J. Phys. C,1970,3,2140; C,1971, 4, 1360; P. K. W. Vinsome and D. Richardson, J. Phys.C, 1971,4,2650; S. P. Singhal, Phys. Rev., 1975, B12, 564. l3 K. R. Schultze and K. Unger, Phys. Stat. Solidi (b), 1974,66,491. l4 J. C. Incson, Thesis (Cambridge, 1971).L. Hedin and S.Lundquist, Solid State Physics, 1969,23 (Academic Press,New York.) l6 N.0.Lipari, Phys. Stat. Solidi (b), 1971, 45, 117. P. W. Anderson, in Elementary Excitations in Solids, Molecules and Atoms, ed. J. T. Devreese, A. B. Kunz and T.C. Collins NATO Advanced Study Institute, Ser. B Physics (Plenum Press, New York, 1974), p. 1. l8 R. R. Dogonadze, A. A. Kornyshev, A. M. Kuznetsov and T.A. Marsagishvili, J.Physique, 38, Colloque C5 (Suppl. No. ll), 1977,35. l9 G. F. Zharkov and Yu. A. Uspenskii, Zhur. Exp. Teor. Fiz., 1971,61,2123; 1973,65, 1460. 2o F. M. Stillinger, Jr. and R. Lovett, J. Chem. Phys., 1968,49,1991. 21 I. Z. Fisher, in Role of Water in Biological Objects, ed. Vuks and Sidova, 1972,3 (LeningradUniversity Press, in Russian). 22 R. R.Dogonadze, in Reactions of Molecules at Electrodes, ed.N. S.Hush (Wiley-Interscience,London, 1971), p. 135. 23 R. R. Dogonadze and A. A. Kornyshev, J.C.S. Farhy 11, 1974,70,1121. 24 F. H. Stillinger, Adu. Chem. Phys., 1975, 31, 1. 25 0. Ya. Samoilov, Structure of Aqueous Electrolyte Solutions and the Hydration of Ions (Con-sultants Bureau, New York, 1965). 26 G. Zundel, Hydration and Intermolecular Interaction (Academic Press, New York, 1969.) 27 R. R. Dogonadze, A. A. Kornyshev and A. M. Kuznetsov, Teor. Mat. Fiz., 1973, 15, 127 (English Translation: Theoretical and Mathematical Physics (U.S.S.R.),1973,15, no. 1). 28 For discussion see, e.g., R. R. Dogonadze and A. A. Kornyshev, Elektrokhim, 1973,9, 1321. 29 R. R. Dogonadze, personal communication. 30 R.R. Dogonadze and A. A. Kornyshev, Doklady Akad. Nauk, S.S.S.R., 1972,207,896. 31 K. Holub and A. A. Kornyshev, 2.Naturforsch. 1976,31a, 1601. 32 P. P. Schmidt and J. M. McKinly, Solid State Comm., 1975, 16, 1161. 33 M. L. Levin and S. M. Pytov, Theory of Thermal Electromagnetic Fluctuations in Electro- dynamics (Nauka, GIFML, Moscow, 1967, in Russian). 34 J. Langer and S.J. Vosko, J. Phys. Chem. Solids, 1960, 12, 196. 35 B. Case in Reactions of Molecules at Electrodes, ed. N. S.Hush (Wiley-Interscience, London, 1971), p. 45. K. HOLUB AND A. A. KORNYSHEV 36 D. G. Knox and J. J. Kozak, Mol. Phys., 1977,33, 811. 37 V. G. Dvali, Dissertation (Kiev, 1976). 38 V. M. Bcrdnikov, personal communication. 39 H. S. Harned and B. B. Owen, The Physical Chemistry of Electrolytic Soiutions (Reinhold,New York, 1950). 40 A. A. Kornyshev, J. Ulstrup and M. A. Vorontyntsev,to be published. 41 Yu. I. Kharkats, A. A. Kornyshev and M. A. Vorontyntsev, J.C.S. Faraday 11, 1975,72,361. 42 M. A. Vorontyntsev,J. Phys. C, to be published. 43 M. Born,2.Phys., 1920,1,45. (PAPER 91452)

ISSN:0300-9238    

DOI:10.1039/F29807600067

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

J.C.S. Faraday ?I, 1980, 76, 82-87 Luminescence and 4A24 2E,2TlAbsorption Spectrum of Cr(urea)& and Al(urea)& :Cr(urea): + BY COLIND. FLINT*AND DAVID J. D. PALACIO Department of Chemistry, Birkbeck College, Malet Street, London WC1 E 7HX Received 22nd March, 1979 A re-examination of the luminescence and absorption spectrum of Cr(urea),13 and Al(urea),13 : Cr(urea)g+ shows that the diluted material contains local concentrations of Cr(urea)g+ ions within which energy transfer processes from majority sites to minority sites occur. These processes also occur in pure Cr(urea),13. The absorption spectrum may be completely analysed as 4A~+2E,2T~ electronic origins together with vibronic origins involving vibrational intervals similar to those ob-served in the luminescence, infrared and Raman spectra.In a previous paper' we reported the absorption and luminescence spectra of Cr(urea),Br, .3H20 and Cr(urea),(NO,), .3H20. The complex absorption and emission spectra of the bromide salt could be interpreted using a conventional Herzberg-Teller vibronic coupling model together with additional vibronic pertur- bations between the vibronic levels of the zE, 2Tl and 4T2states. Radiationless relaxations from the higher excited states to the lower component of the 2Estate were fast. In the nitrate salt this model had to be augmented by the inclusion of energy transfer between five non-equivalent Cr(urea)%+ions. It seemed possible that the structure in the luminescence spectra of Cr(urea)g+ :Al(urea),I,, which was attributed to magnetic coupling within Cr(urea)$+ ion pairs by Koglin et aZ.,2was due to energy transfer between non-equivalent sites.Efficient energy transfer between chromium ions in dilute crystals seemed unlikely, however. The interpretation of the absorp- tion and luminescence spectra of Cr(urea),13 in terms of a strong Jahn-Teller effect in the 2Estate and the observation of 4A2 --+ 4Tzelectronic origins in the absorption spectrum 3* was also inconsistent with our previous work. We have, therefore, measured the absorption and emission spectra and luminescence lifetimes of Cr(urea),I, and Al(urea),13 :Cr(urea)%+ in order to resolve these outstanding prob- lems. We shall argue that the unusual spectroscopic behaviour of the diluted materials arises from an unexpected crystal growth phenomenon.EXPERIMENTAL Cr(~rea)~CI,.3Ha0 was prepared by a standard meth~d.~ The bromide and iodide salts were prepared metathetically and recrystallised from water. Al(ureaJ613was prepared by the method of Koglin et aZ.* Repeated attempts were made to prepare crystals of Al(urea),I, containing isolated Cr(urea);+ ions by allowing aqueous solutions of Al(~rea)~I,and Cr(urea),I, to evaporate slowly in the dark. From these solutions we occasionally obtained individual crystals of essentially pure Al(urea),I, and Cr(~rea)~I,. More frequently we obtained colourless crystals of Al(~rea)~I,which contained inclusions of dark green Cr(~rea)~I~, the size of the inclusions varied from 3 x 1 x 1 mm3 to particles that could only just be resolved under a x 600 microscope.Sometimes apparently homo- geneous pale green crystals were deposited. The luminescence spectra of these crystals 82 C. D. FLINT AND D. J. D. PALACIO suggest that they contain both essentially isolated Cr(urea): -t ions and submicroscopic particles of Cr(urea)& (see below).Luminescence and absorption spectra and chronospectroscopic measurements were measured using the apparatus previously described. The structure and energy levels of these salts were described in a previous paper.l RESULTS PURE Cr(urea),I, LUMINESCENCE SPECTRA The 30 K luminescence spectrum of Cr(urea),13 is shown in fig. 1. This spectrum is essentially identical to that reported by Hansen and Koglin except for the region close to the origin (14 229 cm-l) which is discussed below.The upper component of the 2E state is thermally populated at this temperature and is observed at 14229 cm-l. The number of vibrations expected for the trigonal Cr(urea)g+ entity is so large as to make a detailed vibronic analysis futile. We note, however, that the vibronic sideband is dominated by four intense bands involving vibrational intervals of 173,196,235 and 278 cm-l which must involve 0-Cr-0 and Cr-0-C bending modes. Modes of similar frequency are observed in both the infrared and Raman spectra of Al(urea),13. The relative intensity of the Cr-0 stretching mode at 389 cm-l is lower than that of the corresponding mode in the spectrum of the chloride and bromide salts.To low energy of these skeletal modes a large number of weak-to- medium bands are located which, in many cases, are coincident with internal urea modes observed in the infrared spectrum of the complex and (after allowing for the usual changes on coordination) the free ligand. The spectrum is generally similar to those of the hydrated chloride and bromide salts but is less well resolved. Detailed tabulations of band positions are available elsewhere.6 Careful analysis of the =50 bands observed has failed to provide any evidence for progression-forming modes in this vibronic sideband. Thus any pseudo-Jahn-Teller effect in the 2E state must be extremely weak. Near the origin more than ten medium to weak features are resolved (fig.1). The intensity of the most prominent of these at 14 216 cm-1 varies from sample to sample (it is not mentioned by Hansen and Koglin) and increases markedly on further cooling [fig. 2(a)J. The intensities of the 14 179 and 14 186 cm-1 bands also increase rapidly, they become less well resolved and move slightly to low energy, whilst the 14 200 11 10 13 800 13 600 13 400 I 200 400 600 800 cm-I from origin FIG.1.-514 nm excited 30K luminesmce spectrum of Cr(urea)613. SPECTRA OF Cr(urea),I, AND Al(urea),I, 14 240 14 160 14 240 14 160 cm-l FIG.2-514 nm excited 5 K luminescence spectra near the electronic origin. Laser modulation frequency3 kHz. Cr(~ea)~I~:(a) in-phase emission, (b)in-quadrature emission :(All-aCrs) (~rea)~I~ (c) .x = 2.6 mol % (crystal A) in-phase emission, (d) x = 2.6mol % (crystal A) in-quadratureemssion :(e) x = 3.5 mol% (crystal B) in-phase emission, u)x = 3.5 mol % (crystal B) in-quad-rature emission.14 201 cm-l band loses intensity. At 5 K the lifetimes (and times to maximum intensity) of the origin, 14 216 and 14 180 cm-l bands were 150 (2), 165 (10) and 190 ps (30 ,us), respectively. Clearly the 14 216 and 14 180 cm-l bands correspond to emission from minority species which are populated by energy transfer from the majority species. This is confirmed by the time-resolved spectrum [fig. 2(b)]. There is also some evidence that the origin band contains emissions with at least two slightly different lifetimes. At 30 K the intensity of the emission from the minority species is weak enough for a number of features corresponding to lattice vibrations of the majority species to be observed.The frequencies of these modes correlate well with the zone centre modes observed in the infrared and Raman spectrum of A.l(~rea),I~.~ Al(urea),I, :Cr(urea)a+ LUMINESCENCE SPECTRA The luminescence spectra of two apparently homogeneous pale green crystals of Al(urea),I, containing Cr(urea);+ are compared in fig. 2(c)-(f). The in-quadrature spectrum of sample A shows that the emission at 14 175, 14 180, 14 201, 14 216 and 14 240 cm-1 have different lifetimes from the majority emission at 14 231 cm-l. The 14 175 and 14 180 cm-l features have a 30 ps rise time and a lifetime of 185 ps.The lifetime of the majority emission is ~200ps but is slightly non-exponential. As the temperature is raised, the intensities of the 14 175, 14 180, 14 201 and 14 216 cm-l features decrease. These weaker emissions must correspond to the lower 2E origins of Cr(urea);+ ions at five different crystal sites which are populated by energy transfer. The impurity emissions occur at approximately the same wave- wavenumber as the analogous features in the spectrum of pure Cr(urea),I, (fig. 1). The main band occurs slightly (but significantly) to high energy of its position in the pure compound. The spectrum of sample B near the 2Eorigins is quite different, there being only a single band at 14 231 cm-l together with some very weak lattice vi- brations.The in-quadrature spectrum provides some evidence for a short lifetime component at 14 240 cm-l. We conclude that crystal A contains both bulk Cr(urea),I, entities and more dispersed Cr(urea);+ ions whereas sample B contains mainly isolated Cr(urea);+ ions C. D. FLINT AND D. J. D. PALACIO and/or small aggregates of Cr(urea)g+ ions. The vibronic sidebands of both crystals are almost identical to that of pure Cr(urea),I,. PURE Cr(urea)& ABSORPTION SPECTRA The 5 K absorption spectrum of Cr(urea),I, in the region of the 4Az 32E, 2Tl transitions is shown in fig. 3. The two low energy prominent features are coincident with similar features in the 30 K luminescence and clearly represent the two 4A2 + 'E electronic origins. Weak features at 14 251, 14 271, 14 310 and 14 319 cm-l corre-spond to origins at minority sites.It is tempting to correlate these bands with the 14 180, 14 201 and 14 240 cm-l minority species origins observed in the luminescence spectrum thereby giving a 2E splitting of M 70 cm-l in the minority sites as well as in the majority site. The observed intensity of the 14 229 cm-l origin is strongly dependent on the temperature and nature of the light source because of the intense emission at this wavelength. Comparison of the luminescence and absorption spectra shows that, if we dis- regard intensities for the moment, all of the features up to 14 620 cm-l can be ac- counted for by vibronic origins (involving a vibration with wavenumber identical to those observed in the luminescence spectrum) based on the two majority species 2E origins.Thus we find no reason to invoke a strong Jahn-Teller effect in the 2Estate. The bands at 14 624 and 14 650 cm-l presumably involve vibrations based on one or more 2Tl origins. The most reasonable assignment is that the corresponding origin is at 14 430 cm-1 since the intensity of this band is unexpectedly large for it to be simply a vibronic origin based on a 2Eg electronic origin, Crystal field theory predicts that another 2Tl origin should lie near 14550 cm-l. The feature at 14 606 cm-l is much more intense than expected for a vibronic origin and is therefore probably a second 2Tl origin. Using these two 2Tl origins and the two 2Eorigins together with the vibrational intervals and vibronic intensities observed in the lumi- nescence spectrum, it is possible to account for every definitely observed feature between 14 320 and 15 550 cm-l.The large number of vibronic features expected in this region together with the increasing distortion of the spectrum by antiresonance 14 200 14 400 14 600 14 800 15 000 15 200 15 400 cm-1 FIG. 3.-5K single crystal absorption spectrum of Cr(urea)&. The apparent intensity of the absorption band at 14229cm-I is greatly reduced by the intense emission at this wavenumber. At higher temperatures, where the emission is weaker, the 14 229 and 14 299 cm-I bands have com-parable intensity (see inset). SPECTRA OF Cr(urea),I, AND Al(urea),I, with the underlying 4T2gcontinuum makes the location of the third 2Tl origin un- certain.The most reasonable assignment of this origin is the weak sharp band at 14 990 em-l. The strong broad feature at 15 210 cm-l is then 14 990+235. Alter-native assignments are discussed in ref. (6) where detailed tabulations of band positions are given. Based on this analysis each of the five 4A2-+ 2E, 2Tl origins occur in a similar position to the corresponding origins in the hydrated bromide salt? DISCUSSION The chronospectroscopic measurements on Cr(urea),I, show that the lumi- nescence spectrum in the region of the 2E+ 4A, origin is influenced by emission from minority sites which are excited by energy transfer from the predominant site. These minority emissions are also observed in some Al(urea),I3Cr3+ crystals con- taining a few per cent of Cr3+ ions.Energy transfer would be rather inefficient in these crystals if the Cr(urea)g+ ions were isolated and this, together with the unusual crystal growth phenomena described in the experimental section, suggests that some apparently dilute crystals contain submicroscopic local concentrations of Cr(urea)%+ ions. The spectroscopic and energy transfer behaviour of the Cr(urea)a+ ions within these local concentrations are similar to those of pure Cr(urea),I,. The perceptible shift in the position of the most intense origin and the lower (but variable) intensity of the minority site emissions in the diluted material indicates that these crystals also contain Cr(urea):+ ions which are not in these local concentrations.We shall refer to these as "isolated " Cr(urea)g+ ions although close similarity of the spectra and lifetimes of the pure and " diluted " crystals means that we cannot distinguish truly separated Cr(urea)g+ ions from pairs or other small aggregates. We emphasise, however, that the spectra of the "isolated " ions provide no evidence for interionic interactions. Comparison of our spectra with that of a Cr3f(26 mol %) :Al(urea),I, crystal [fig. 7 and 8 of ref. (2)j indicates that Koglin et al. obtained significantly better spectral resolution. This is due in part to the greater dispersion of their mono- chromator but the crystals employed may also have given better line widths. Features at 14 278, 14 237, 14 217, 14 168 and 14 095 em-I were attributed to mag- netically coupled pairs.The 14 278 em-l band was also present weakly in the spectra of our pure and diluted crystals at 30 K but disappeared on further cooling. The 14 237 cm-1 band was not observed in the pure compound but was observed in the diluted crystals where it has a shorter lifetime than the most intense band. The 14 217 cm-l band appears strongly in the luminescence spectra of the pure and diluted compounds where the species responsible is populated by energy transfer and has a longer lifetime than the most intense band. The 14 168 and 14 095 cm-l bands occur as weak features which have comparable lifetime to the most intense band and are not strongly temperature dependent.We therefore attribute them to part of the phonon sideband. The 14 180 cm-l band in our spectra is not reported in ref. (2). This may be because of the different crystal employed or because the temperature of the sample used by those authors (as evidenced by the intensity of the anti-Stokes emission) was >30K. We conclude that all of the features assigned as due to magnetically coupled ions are either phonon sidebands or minority site traps in Cr(urea),I,. Combining these results with those of our previous study on the hydrated chloride and bromide and the anhydrous nitrate provides a consistent interpretation of the absorption and emission spectra of these species. Since the iodide and nitrate salts C. D. FLINT AND D. J. D.PALACIO are prone to disorder we suggest that these salts are avoided in future spectroscopic studies. We thank the S.R.C. and the London University Central Research Fund for grants for the purchase of equipment. Some preliminary measurements on these systems were carried out during 1971-4 by Paul Greenough and A. Peter Matthews. C. D. Flint and D. J. D. Palacio, J.C.S. Furuhy 11, 1979, 75,1159. E. Koglin, W. Krasser, G. Wolff and H. W. Nurnberg, 2.Nuturforsch. 1974,29a, 211. H. J. Schenk and W. H. E. Schwarz, Theor. Chim. Am., 1972,24,225. K. H. Hansen and E. Koglin, Theor. Chim. Actu., 1972,24,216. W. G. Palmer, Experimental Inorganic Chemistry (Cambridge University Press, London, 1954).D. J. D. Palacio, Thesis (University of London, 1977).'W. Krasser, E. Koglin, G. Wolff and H. W. Niirnberg, 2.Nuturforsch., 1974, 29a, 219. (PAPER 9/483)

ISSN:0300-9238    

DOI:10.1039/F29807600082

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

J.C.S. Faraday 11, 1980,76,88-95 Non-rigid Molecules Part 4.t-Hydrogen Atom Scrambling in the Mass Spectra of Hydrocarbons BY JOHN DALTON* AND LIONELR. MILGROM Department of Chemistry, City of London Polytechnic, 31 Jewry Street, London EC3N 2EY Received 28th September, 1978 Partial internal energies and H atom distributions are calculated uia first-order perturbation theory for the ions CnH:n+~-m(n = 2,4 ; m = 0, 2n+ 1) by considering their H atoms to form a delocalized system. Recently, Woolley has argued that molecular shape is not a property of molecular potential-energy eigenstates.l Indeed it can only be associated with them via the ad hoc hypothesis of the Born-Oppenheimer approximation.2. This procedure is open to the greatest objection when it is used to assign precise molecular structures to excited eigenstates of isolated small molecules or ions in dilute gases and molecular beams?. These conditions resemble those within the ion source and flight tube of a mass spectrometer, where hydrogen and carbon scrambling have been well-documented phenomena for over a decade 5u-c9 although the mass spectrometer prepares (almost-) pure states of the kinetic rather than potential energy.The mechanistic interpretation of this scrambling has generally invoked o-bond delocalisation or atomic rearrangement through high energy structural configurations of the ions 5a before fragrnentation. For example, deuterium-labelled butyl ions from t-butyl compounds underwent complete HID scrambling before methane Mechanistically this was interpreted in terms of 1,2-hydride shifts. Carbon scrambling has also been observed in l3C-labelled butyl ions from n-butyl iodide and this was rationalised in terms of isomerisation to the most stable tertiary structure.Similarly, hydrogen and carbon scrambling have been observed in aromatic systems.lo'l Carbon scrambling here was thought to involve prismane and benzvalene intermediates by analogy with known photochemical transforma- tion~.~~Hydrogen scrambling was seen in terms of localised C-H bond breaking and reformati~n.~~ More recently, it has been shown that hydrogen scrambling may take place independently from, or even without, carbon skeleton rearrangement,5u* * 14-17 We offer below an alternative description of the process of H atom scrambling in which the H atoms are considered to be delocalised over a spatially fixed set of " C-H bond " potential wells.A Consider the HCC angle bending vibrations of a molecular fragment HCCH in the eclipsed conformation. Most of the motion is localised in the lighter H nuclei and occurs at rates slow enough to allow the electrons to track the nuclear motion. Accordingly, the H nuclear wavefunctions, with respect to an appropriate bending t For part 3 see J. Dalton and C. A. McAuliffe, J. Organometallic Chem., 1972,39, 251. 88 J. DALTON AND L. R. MILGROM coordinate, will be roughly as shown in fig. 1. In some respects the situation shown in fig. 1 resembles that of two electrons in adjacent carbon 2pZ atomic orbitals.However, there is one major difference, at least if the HCCH fragment is part of a molecular ground state. Any interaction energy between the nuclear wavefunctions of fig. 1 is too small to allow chemically significant mixing of the H nuclear wave- functions on the two C atoms. In other words, a fragment HXCCYD remains distinguishable from DXCCYH. In contrast, chemically significant mixing of adjacent 2pZ electrons does occur. (" Chemically significant " in the sense that an accompanying energy change, the delocalisation energy, can in principle be calculated by appeal to a reference state of the same system.) 41 = 0 QZ = 0 (Ql942) FIG.1.-Potential energies (soIid) and wave functions (dotted) as a function of generalised bending coordinate (4)for adjacent H nuclei.However, experiment suggests (vide supra) that interchange of H and D nuclear wavefunctions can occur in electron-impact mass spectrometry, so that HXCCYD is therefore not always distinguishable from DXCCYH. By analogy with the electronic case, we suppose that electron-impact ionisation modifies the nuclear wavefunctions and potential wells of fig. 1 in a way which introduces a favourable delocalisation energy. For example, by excitation to higher- amplitude bending modes with enhanced tunnelling frequencies or by reduction of the bending force constant to a value allowing greater interaction between adjacent potential functions. We further assume that the distribution of C-H potentialwells is unaffected by this process, so that the H nuclei become a set of more or less freely moving particles over a fixed framework of C-H potential wells.It seems natural to base the detailed description of such a system on one of the well-established treatments of electron delocalisation modified in the light of the differences between H nuclei and electrons. For example, the maximum occupancy of each delocalised H nuclear orbital will be one rather than two, provided that these functions are obtained as linear combinations of the basis set. Thus LCAO electron theory, in which doubly occupiable electron space-orbitals are obtained, should provide suitable models, mutatis mutandis. For the present calculations it was convenient to select Huckel theory as the model.This simplified the calculations by virtue of the neglect of direct H nucleus-H nucleus interaction terms in the Hamiltonian and additionally by the neglect of overlap between different basis functions. The basis functions themselves resemble those 90 NON-RIGID MOLECULES within the potential wells of fig. 1. The neglect of differential overlap allows us to avoid specifying precise nodal patterns. Their energies are given by integrals of the form ai = 1@iH$tdz, analogous to the Coulomb integrals of Huckel theory. All a, are assumed equal. The interaction energy between the ith andjth basis functions will be given by integrals of the type bij = [JIIiY$jdz. In guessing their magnitudes we have used the analogous resonance integrals of Huckel theory as a guide.Thus all bij = 0 if i and j are on non-bonded atoms. On the other hand, bij = b (and assumed constant) where i andj are on the same atoms. When i andj are on adjacent, bonded carbon atoms the numerical value of bij presumably depends upon the angular separation of the i andj potential wells when projected parallel to the Ci-Cj bond. For the purposes of the present calculations we simplify the parameter scheme still further by taking b,, = b or 0 as this projected angle is, respectively, less than or greater than 90'. With these assumptions and the numbering system of fig. 2(a)the energy matrix (1) is readily derived for ethane. Its diagonalisation gives the effects of these interactions correct to the-first order.The six eigenvalues (table 1)represent the energies of each * (4 FIG.2.Basis function numbering and configurations for the reference states of C2Hi (a),C3HG (b)and GHI, (c). J. DALTON AND L. R. MILGROM of the six hydrogen nuclei in the scrambling state and the corresponding eigen- vectors (table 1) represent their spatial distribution over the carbon atom core. For example, the “ C-H bond energy” calculated for the species C2H+ is (a+4b). This shoufd be compared with the vahe (a) for a single C-H bond energy in the reference state. The scrambling state is more stable by an energy of 14bl. The eigenvector corresponding to this eigenvalue has equal coefficients over all six potential wells of the core. The single H atom in the scrambling state of C2H+ can thus be visualised as extending around the core like a (nodeless) sausage skin.‘a b b b 0 b‘ babbbO bbaObb bbOabb Obbbab bObbba. H nuclei in higher energy orbitals are more or less similarly distributed but with a number of nodal planes intersecting the “sausage skin”. These nodes, whose number increases generally with the energy of the orbital, are a unique feature of the present model. They might not be unconnected with the fragmentation l9 reactions of the central core. By analogy with Huckel theory, the numerical values of the coefficients of occupied orbitals may be used to calculate H nuclear densities at the potential wells and ‘‘skin thicknesses ” (which may be negative) between them.TABLE 1.-EIGENVALUESAND EIGENVECTORCOEFFICIENTS FOR CsHZ WITH THE CONFIGURATION AND NUMBERING SCHEME OF FIG. 2(a) eigenvector coefficients eigenvalue 1 2 3 4 5 6 1-2b -0.28 -0.30 0.58 0.58 -0.28 -0.30 a-2b -0.51 0.49 0.01 0.01 -0.51 0.49 a -0.05 -0.71 -0.02 0.02 0.05 0.71 a -0.71 0.05 -0.02 0.02 0.71 -0.05 a 0.02 0.02 -0.71 0.71 -0.02 -0.02 a+ 4b 0.41 0.41 0.41 0.41 0.41 0.41 The results of similar calculations for propane and n-butane are summarised in tables 2 and 3. In each case the most stable rotamer of the neutral molecule has been chosen as the reference state. The numerical values obtained using the present parameter scheme clearly depend upon, irtter alia, the assumed rotational conforma- tion.The extent of this dependence has been investigated for n-butane by repeating the calculations for a further three conformations of the carbon core. The resulting eigenvalues are plotted (fig. 3) as a function of the angle between the terminal C-C bonds when projected onto a plane perpendicular to the central C-C bond. The correlations were obtained by following the nodal patterns during rotation. They must be regarded as tentative in the absence of character tables for the appropriate permutation group^.^ O On the simplest view of electron-impact-induced fragmentation patterns an energy of n(a) is required to form C,H&,, from C,H,+. The relative abundances NON-RIGID MOLECULES of the species (n = 0-q) should then reflect the distribution of excess energy over the population of ions C,HZ [fig.4(a)]. In the present Huckel-like treatment this n energy would be 2: El, where El is an eigenvalue of the appropriate matrix. In i= 1 general IZEJ < lnal(0 < n < q) so that fragmentation would be easier in the scram- bling state [fig. 4(b)]. This prediction would be rather difficult to test. TABLE2.-EIGENVALUES AND EIGENVECTOR COEFFICIENTS FOR C3H; WITH THE CONFIGURATION NUMBERING AND SCHEME OF FIG. 2(b) eigenvector coefficients eigenvalue 1 2 3 4 5 6 7 8 a-2.41 b -0.35 0 0.35 0.50 -0.50 -0.35 0 0.35 a-1.60b -0.07 0.58 -0.07 -0.39 -0.39 -0.07 0.58 -0.07 a-b 0.39 0.17 -0.56 0 0 -0.39 -0.17 0.56 a-b 0.42 -0.55 0.13 0 0 -0.42 0.55 -0.13 U- 0.32b 0.41 -0.15 0.41 -0.38 -0.38 0.41 -0.15 0.41 a+ 0.41b 0.35 0 -0.35 0.50 -0.50 0.35 0 -0.35 a+ 2b -0.41 -0.41 -0.41 0 0 0.41 0.41 0.41 a+ 3.92b 0.28 0.37 0.28 0.45 0.45 0.28 0.37 0.28 A more realistic view of fragmentation energies would include any contribution from the internal energy of the neutral fragment.Thus elimination of dihydrogen would require less energy than the separate elimination of two hydrogen atoms. In this connection it is interesting that the process C2HZ + C,H; +(H,?) dominates the 70 eV spectrum of ethane, where the two most accessible H atoms are predicted, with the present parameters, to occupy a degenerate orbital. TABLE3.-EIGENVALUES AND EIGENVECTOR COEFFICIENTS FOR c,Ht,) WITH THE CONFIGURA- TION AND NUMBERING SCHEME OF FIG.2(C) eigenvector coefficients eigenvalue 1 2 3 4 5 6 7 8 9 10 a-2.62b -0.26 0 0.26 0.43 -0.43 -0.43 0.43 0.26 0.26 0 a-1.63 0.43 0 -0.43 -0.26 0.26 -0.26 0.26 0.43 -0.43 0 a-1.476 -0.10 0.54 -0.10 -0.30 -0.30 0.30 0.30 0.10 0.10 -0.54 a-1.15b -0.23 0.61 -0.23 -0.12 -0.12 -0.12 -0.12 -0.23 -0.23 0.61 a-0.46b -0.36 0.22 -0.36 0.31 0.31 -0.31 -0.31 0.36 0.36 -0.22 a-0.38b -0.43 0 0.43 -0.26 0.26 0.26 -0.26 0.43 -0.43 0 a+ 0.48b 0.36 0.14 0.36 -0.33 -0.33 -0.33 -0.33 0.36 0.36 0.14 a+0.62b 0.26 0 -0.26 0.43 -0.43 0.43 -0.43 0.26 -0.26 0. a+2.946 -0.33 -0.40 -0.33 -0.25 -0.25 0.25 0.25 0.33 0.33 0.40 a+3.67b 0.26 0.34 0.26 0.36 0.36 0.36 0.36 0.26 0.26 0.34 Much of the impetus for the present approach comes from the results of electron- impact mass spectrometry of partially deuterated hydrocarbons.The description in the present terms of H/D scrambling in such systems encounters a difficulty which has no analogue in delocalised electron theory. Briefly, the construction of linear J. DALTON AND L. R. MILGROM 1 2 4.3 -...... *"-. *. ...*. '-.... ..... I I I 1 0 60 120 180 FIG.3.-H atom eigenvalues for n-C4H:, as a function of the projected angle between the C(l)-C(2)and C(3)-C(4) bonds. The plane of projection is the perpendicular bisector of C(2)-C(3) and the configuration of fig. 2(c) corresponds to an angle of 0". combinations of nuclear basis functions in partially deuterated molecules can result in atomic wavefunctions which represent neither H nuclei nor D nuclei but inter- mediate species to which we are reluctant to attach physical meaning.N= 0 \N=l Y=1 U=2 i I 0 : 3 4 5.6 7 8 FIG.4.-Relative abundances of the ions C3H+s-N against ion excess energies (in units of a with the arbitrary assumption 4b = a) for the localised (a) and scrambling (b) states in the simplest case (see text). One approach to this problem will be illustrated by considering the species CH,CD;. Its energy matrix (2) resembles that of CH,CH: (1) except that it is constructed from three different basis functions : H nuclei (rows/columns 1-3)'D nuclei (rows/columns 4, 5) and a "vacancy " (row/column 6).Matrix elements between distinguishable nuclei (e.g., H and D) are set equal to zero to deal with the NON-RIGID MOLECULES difficulty outlined above. But the “vacancy ” is allowed to retain matrix elements with any basis function subject to the constraints of the parameter scheme. Thus distinguishable nuclei, which are not allowed to mix directly, are interchanged via the “vacancy ” (table 4). A corollary is that HID scrambling should not occur in species such as CH,CD; which lack such a vacancy.* abbOOO TABLE4.-EIGENVALUES AND EIGENVECTOR COEFFICIENTS FOR CzHsD (SEE TEXT) eigenvector coefficients eigenvdue 1 2 3 4 5 6 a- 1.OOb 0.00 -0.71 0.71 0.00 0.00 0.00 a- 1.00b 0.00 0.00 0.00 -0.71 0.71 0.00 a-0.51b -0.74 0.19 0.19 -0.30 -0.30 0.46 a+1.51b -0.43 -0.32 -0.32 0.52 0.52 0.26 af2.84b 0.33 0.47 0.47 0.29 0.29 0.53 In conclusion, we note that the extension to non-identical nuclei enables the present method to deal with the scrambling of carbon or other heavier nuclei in principle, although the matrices (and their interpretation) rapidly become unwieldy as the molecular complexity increases.J. D. thanks Dr. R. C. Dougherty for stimulating discussions. We are most grateful to a referee for his detailed and sympathetic comments. R. G. Woolley, J. Amer. Chem. Soc., 1978,100, 1073. M. Born and J. R. Oppenheimer, Ann. Phys., 1927, 84,457. C. A. Coulson, Valence(Clarendon Press, Oxford, 2nd edn, 1961), chap. 1and 3, p. 56. R.G. Woolley, Adv. Phys., 1976,25, 27. (a) D. H. Williams (Senior Reporter), MQSSSpectrometry (Specialist Periodical Reports, The Chemical Society, London, 1971), vol. 1, p. 53 ; (b) R. A. W. Johnstone (Senior Reporter), Mass Spectrometry (Specialist Periodical Reports, The Chemical Society, London, 1975),vol. 3 ; (c) R. A. W. Johnstone (Senior Reporter), Mass Spectrometry (Specialist Periodical Reports, The Chemical Society, London, 1977), vol. 4. J. T. Bursey, M. M. Bursey and D. G. I. Kingston, Chem. Rev., 1973, 73, 191.’See ref. (54, p. 60 and B. Davis, D, H. Williams and A. N. H. Yeo, J. Chem. SOC.B, 1970,81.* G. J. Karabatsos, R. A. Mount, D. 0. Rickter and S. Meyerson, J. Amer. Chem. Sac., 1970, 92, 1248. See ref. (5a),p. 61 and W. G. Cole and D.H. Williams, Chem. Comm., 1969,784 ; G.A. Smith and D. H. Williams, J. Chem. SOC.B, 1970,1529. lo K. R. Jennings, 2.Naturforsch., 1967,22a, 454. l1 I. Horman, A. N. H. Ye0 and D. H. Williams, J. Amer. Chem. Soc., 1970, 92,2131. l2 R. Dickinson and D. H. Williams, J. Chem. SOC.By 1971, 249. * We thank a referee for drawing our attention to the experimental verification of this point. J. DALTON AND L. R. MILGROM l3 D. Bryce-Smith and H. C. Longuet-Higgins, Chem. Comm., 1966,593. 14See ref. (5c), p. 49 and A. Venema and N. M. M. Nibbering, Organic Mass Spectrometry,1974,9,628. l5 A. Venema, N. M. M. Nibbering and Th. J. de Boer, OrganicMass Spectrometry, 1970,3,1589. l6 R. J. Dickinson and D. H. Williams, J.C.S. Perkin 11, 1972,1363. J. H. Bowie, P. Y. White and T. K. Bradshaw, J.C.S. Perkin 11, 1972, 1966. l8 L. Pauling and E. B. Wilson, Introduction to Quantum Mechanics (McGraw-Hill, New York, 1935), chap. VI. l9 Compare, for example, M. Born, Atomic Physics (Blackie and Son, London, 1969), section X, 9 ; pp. 347-351. 2o H. C. Longuet-Higgins, Mol. Phys., 1963,6,445. (PAPER 8/1712)

ISSN:0300-9238    

DOI:10.1039/F29807600088

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

J.C.S. Farahy 11, 1980, 76,96-100 Electron Paramagnetic Resonance and Nuclear Magnetic Resonance Studies of Lipid-Water Systems BASOSI,ELENAGAGGELLIBY RICCARDO AND ENZOTIEZZI* Institute of General Chemistry, University of Siena, Pian dei Mantellini 44, 53100 Siena, Italy Received 9th April, 1979 The MnWecithin aqueous dispersion has been investigated by means of e.p.r. spectra and of nuclear relaxation rates of water protons. Three different cases have been studied, namely (a) the integral system having only external MnII ions, (b) sonicated dispersions with MnII ions inserted in the vesicles and (c) the vesicles having only internal MnII ions. A relaxation model has been proposed which takes into account the existence of a randomlydistributed electron spin relaxation time and its effect on the nuclear relaxation rates. The relevance of metal-lipid interactions has been emphasised.The structural and dynamicfeatures of the system investigated have been interpreted by the combined analysis of the e.p.r. lineshapes and of the paramagnetic contributions l/Tlp and 1/Tz,to the water proton relaxation rates. Mn” has been used previously in the study of interactions between metal ions and micellar or lamellar systemd The aim of this paper is to extend a combined e.p.r. and n.m.r. analysis using the Mnl* probe to phospholipid aqueous dispersions. Moreover, the relevance of outer-sphere metal coordination, as pointed out by Oakes for micelles, is considered. Two types of dispersion have been used, in order to have two membrane models : those where the lipid is dispersed mechanically into coarse particles and those where the lipid is dispersed by ultrasonic irradiation to give single spherical bilayer vesicles.These mesomorphic lipid-water phases provide a useful model for studying ion diffusion across cell membranes which may involve the interaction of ions with polar regions of the membrane. These systems have already been studied by proton relaxa- tion enhancement (p.r.e.),” by high resolution n.m.r. (13C, 31P)3 and by novel lH-n.m.r. method^.^ Moreover, the effects of small amounts of metal ions have been inve~tigated.~ When manganous ions are inserted in the vesicles, the exchanging water molecules act as a double probe, giving information on the environment of the paramagnetic metal probe.EXPERIMENTAL Egg yolk lecithin was obtained from Merck. The dispersions were made by dissolvingthe lipid in CHCI3, evaporating the solvent under nitrogen and adding deuterium oxide (99.75 % D20). 10cm3 of the coarse lecithin dispersion in D2O were sonicated for 20min under a nitrogen atmosphere using the MSE-150 ultrasonic disintegrator in an ice-cooled glass tube. The concentration of MnlI was adjusted by adding calculated volumes of stock solutions of Mn(C104)2 (Alpha Inorganics). 3-5 fold excess (in terms of exchanging capacity) of Chelex 100 (Bio-rad) was added to the sonicated dispersion to exchange Mn2f in the external solution by Na+. The sample was shaken for 10min and 30.5 cm3 solution was decanted for n.m.r.and e.p.r. measurements. 96 R. BASOSI, E. GAGGELLI AND E. TIEZZI Nuclear spin relaxation times TI and T2 were measured by means of a Bruker WH-90 f.t.-n.m.r. spectrometer operating at 90 MHz. The resonance frequency of the deuterium nucleus was used as an internal lock. Temperature was varied by means of a Bruker temperature control unit ; its accuracy was & 1 K. Spin-lattice relaxation times were obtained from partially relaxed proton spectra using the (180-z-90-t), pulse sequence. TI was evaluated by a least-squares analysis of the exponential curve : the values were accurate to within & 5 %. The data are the mean value of at least three measurements. E.p.r. spectra were registered with a Bruker ER 200 tt spectrometer operating in the X-band (9200 MHz).Q-band spectra (34 350 MHz) were recorded with a Varian V-4651 microwave bridge, provided by the Institute of Physics, University of Parma. RESULTS AND DISCUSSION The e.p.r. data have been interpreted in terms of a relaxation model taking into account a distribution of 7, The nuclear relaxation rates T;:2";'and have been analysed by considering the electron spin relaxation time z, as an actual correlation time for the nuclear relaxa- ti~n.~, Fast exchange conditions hold; thus TF: and 7';: are determined bylo the relative weights of the dipolar and scalar contributions, which, in turn, are FIG.1.-Experimental e.p.r. spectra of mol dm-3 MnII in lecithin (25 % by weight aqueous dispersions) at room temperature and pH = 7; (a) integral, (6) sonicated, (c) sonicated with external Mn2+ions replaced by Na+ ions.11-4 E.P.R. AND N.M.R. OF LIPID-WATER SYSTEMS affected by the magnitude of 7,. The random distribution of z,in the systems under study gives rise to z,values above and below the reorientational correlation time 7,. The temperature dependence of the electron spin relaxation in sonicated dispersions displays divergence from the behaviour of the free manganous ion, the linewidths of the lipid system being broader than those of the free ion. Moreover, a 50 % e.p.r. intensity loss is present. Both findings indicate the presence of interactions via water between the metal ion and the lipid molecules,i1-12 thus indicating the presence of the equilibrium suggested by Oakes for the case of Mn"-micelle systems.Furthermore zk, the mean jump time of solvent molecules between various con- figurations, is temperature-dependent, giving rise to high-temperature line-broadening caused by the averaging out of crystal field sites which were isolated in the low temperature limit. This being the case, the e.p.r. linewidth displays a smoother decay in the Mn"-lecithin system than in the absence of the ligand. The MnII-lipid system has also been investigated by analysing the following three situations : (i) the integral system in which the Mn2+ ions interact with the external surface of large '' onion-like " structures ; (ii) the sonicated system in which the Mn2+ ions interact with both the internal and external surfaces of single bilayer vesicles, having a much smaller diameter and a much faster tumbling rate than those of the integral dispersion; (iii) the sonicated system, as in (ii), but in which the external Mn2+ ions are mostly replaced by ionic exchange with Na+ ions and only the inter- action with the internal surface of the vesicle is possible.Fig. 1 shows the e.p.r. lineshape for cases (i)-(iii). The lineshape analysis indicates the presence of broad background signals in every case and of spectra which display more or less strong deviations from a single- lorentzian lineshape represented by a single average z.f.s. term. The extent of devi- ation can be evaluated by the greater amplitude of the fifth h.p.f.line with respect to the fourth.13 In this connection, the strongest deviation is found in case (ii) [case (b)in fig. 11 while a similar lineshape is evident in cases (i) and (iii). A single average z.f.s. term cannot be assumed in these cases and the lineshape Y'(H)can be accounted for by a distribution of several lorentzian lineshapes having different widths :6 Y'(H)= EPkY(H),. When the system passes from (i) to (ii) [from (a) to (b) in fig. 11 the enhanced motional freedom at the molecular level gives rise to the strongest deviations from the single-lorentzian case. Since 7, is expected to be z 10-9-10-10s, the lineshape analysis requires that Tk > s and z,< zk. The change in lineshape from (a) to (b)may be ascribed to a slight shortening of the rotational correlation time which results in a less effective averaging process of the crystal field sites.When only the internal Mn2+ ions are left to interact with the lipid molecules [case (c) in fig. 11 the e.p.r. lineshape, together with an obvious drastic intensity loss, is similar to case (a), which is consistent with a small lengthening of the rotational correlation time. This finding is not surprising : the reorientational rate reflects how the solvation environment affected by the metal electric field fits the structural order in the bulk solvent; thus it is consistent that a slightly longer rotational time is expected in the internal solvent, which is relatively more ordered than the external, because of the greater curvature of the charged surface.The paramagnetic contributions to the water proton relaxation rates are shown in table 1 at two pH values. In the integral system [case (i)] the relative magnitudes of Tit and TF: indicate an entirely dipolar contribution to Tland an entirely scalar contribution l4 to T2 at both pH values. The dipolar term is insensitive to changes value is found at pH = 7 than at pH = 3, whichin pH; 7';: greaterawhereas R. BASOSI, E. GAGGELLI AND E. TIEZZI reflects a metal-ligand binding favoured by raising the pH. In the sonicated dispersion [case (ii)] Tc: increases and T;: falls. Since the concentration of para- magnetic ions is the same, the following events may account for the effect : (a) change in the medium's viscosity ; (b) change in the rotational correlation time ; (c) change in the electron spin relaxation time.1.-PARAMAGNETICTABLE CONTRIBUTIONS TO WATER PROTON RELAXATION RATES IN MnII-LECITHIN AQUEOUS DISPERSIONS a Tit IS-' T;: Is-' cad pH=3 pH=7 pH=3 pH=7 (9(ii) (iii) 3.5 7.1 3.4 3.2 5.6 3.1 12.3 7.2 9.5 17.3 12.1 14.4 (1 Lecithin was 25 % by weight in 99.75 % D20; [Mn2+]= loF4mol dm-3 ; T = 310 K. (i) is the integral dispersion, (ii) the sonicated dispersion and (iii) the sonicated dispersion in which the external Mn2+ ions are replaced by Na+ ions. (a) and (6) could explain the T;: enhancement but are not consistent with the T;: behaviour, so event (c) indicates most suitable interpretation, with the aid of the e.p.r.results. When the Mn"-lecithin system undergoes sonication the e.p.r. line- shape is described by the Y(H)function. Since several zs values must be considered, it follows that some water molecules may be relaxed in environments characterized by woz, < 1, which gives rise to the observed effect. If complete or partial averaging of the z.f.s. terms occurs it takes a much shorter time than the nuclear relaxation time: in this case the water molecules sense an averaged 2, value. At pH = 3 the TL: = T;: condition is reached because of the smaller scalar contribution to the unsonicated dispersion. The relationship between nuclear and electron spin relaxation analysis is ratified by the data obtained in case (iii). The decrease in Mn2+ concentration should result in reduced paramagnetic contributions.This is the case for Tc:, while an even greater TFi value is found, which reflects the similar trend displayed by the e.p.r. lineshape in returning to the original conditions. This finding demonstrates the relevance of the z, distribution and of the averaging of the z.f.s. terms in determining the scalar contribution to the nuclear relaxation rates. The role of T, as a correlation time in determining the nuclear paramagnetic relaxation rates and the analysis of the z, distribution in macromolecular systems acquire even more significance in the light of the novel derivation of the Solomon- Bloembergen-Morgan equations, which focuses on the metal ion rather than on the ligand nuclei, including ligand-field terms in the TI expression.Thanks are due to Dr. G. Sabatini and Mr. F. Brogi for their helpful technical assistance. J. Oakes, J.C.S. Faraday 11,1973, 69,1321. P. W. Nolden and T. Ackermann, Biophys. Chem., 1975,3,183. P. W. Nolden and T. Ackermann, Biophys. Chem., 1976,4,297 and references therein. 4G. R. Hunt and L. R. H, Tipping, Biochim. Biophys. Acta, 1978, 507, 242 and references therein. E.P.R. AND N.M.R. OF LIPID-WATER SYSTEMS S. A. Simon, L. J. Lis, J. W. Kauffman and R. C. MacDonald, Biochim. Biophys. Actu, 1975, 375, 317 and references therein. ti L. Burlamacchi, G. Martini, M. F. Ottaviani and M. Romanelli, Adv. Mol. Relax. Proc., 1978, 12, 145.’R. Basosi, F. Laschi, E. Tiezzi and G. Valensin, J.C.S. Furaduy I, 1976,72, 1505. ti R. Basosi, N. Niccolai, E. Tiezzi and G. Valensin, J. Amer. Chem. SOC.,1978, 100, 8047. S. H. Koenig, J. Magnetic Resonance, 1978, 31, 1. lo T. J. Swift and R. E. Connick, J. Chem. Phys., 1962,37,307. L. Burlamacchi and E. Tiezzi, J. Phys. Chem., 1969,73, 1588. L. Burlamacchi, G. Martini and E. Tiezzi, J. Phys. Chem., 1970,74,3980. l3 M. Romanelli and L. Burlamacchi, MoZ. Phys., 1976, 31, 115. l4 W. G. Espersen and R. B. Martin, J. Phys. Chem., 1976, 80, 116. (PAPER 91568)

ISSN:0300-9238    

DOI:10.1039/F29807600096

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

J.C.S. FLZ~UJJII,1980,76, 101-103 Atomization Energies of Complex Gaseous Yttrium Carbides BY KARLA. GINGERICH*AND REZA HAQUE Department of Chemistry, Texas A & M University, College Station, Texas 77843, U.S.A. Received 30th April, 1979 The atomization energies, of the new molecules YC3, YC5 and YC6have been determined by Knudsen cell mass spectrometry as 1805 t30, 3081 3-35 and 3781 rt: 60 kJ mol-', respectively. The trends observed in the atomization energies for polyatomic yttrium carbides follow those of the polyatomic carbon molecules with equal numbers of atoms. Previous knowledge of gaseous yttrium carbides is limited to the molecules YC2 and YC4.2 The existence of stable molecules YC and YC3 has also been predicted. The recent observation of gaseous CeCS and CeC6 suggested that such higher polyatomic transition metal carbides may have a wider occurrence.The investigation of new yttrium carbide molecules which is reported here has been part of a current research programme aimed at the identification of new MC,, molecules, including those of d-block transition metals such as scandium and the actinides, e.g., uranium and thorium.' These investigations are expected to yield atomization energies and possibly structural information on which empirical cor- relations may be based. This will permit the prediction of the stability and possibly molecular structural properties of a large number of yet unknown gaseous metal carbides. In the present investigation the atomization energies of the new molecules Ye3, YC, and YC6 have been determined along with those of the known molecules YC2 and YC4.EXPERIMENTAL The Knudsen effusion technique, combined with mass spectrometric analysis of the equilibrium vapour, was used in this investigation. The instrument and the experimental procedure have been described elsewhere.8* The sample, contained in a graphite Knudsen cell, consisted of a scandium-yttrium-rhodium mixture, to which excess graphite was added, to insure unit activity of carbon, i.e., a = 1.0. A small amount of silver served for calibration purposes. An outer tantalum cell minimized the evaporation losses of the graphite cell during the experiments. The temperature was measured with a calibrated optical pyrometer by sighting into a black body hole at the bottom of the outer cell.The ion currents were measured using an electron energy of 20 eV. The species were identified by their mass-to-charge ratio, shutter profiles and ionization efficiency. Appearance potentials of yttrium and the yttrium carbides, as obtained by the linear extrapolation method (in eV) using that of Ag+ (7.57 eV) as a reference,l0 are : Y+, 6.4k0.6; YC;, 6.320.8 ; YC;, 6.6+ 1.2 and YC;, 7.2f 1.0. The values for YC; and YC; compare with the corresponding literature values of 6.8f0.3 or 6.7f0.3 for YC; and 7.0k0.3 for YC;. No meaningful values could be obtained for YC; and YC: due to their verysmall ion currents. The value 13.5+ 1.0eV obtained for YCf indicates that this ion was mainly produced by fragmentation, presumably of YC2 and it is similar to the values obtained in 101 ATOMIZATION ENERGIES OF Yc, previous studies: 13.420.5 and 14.0+1.2 A very small tail at the low energies of the ionization efficiency curve with an apparent appearance potential of 8f2 eV suggested also the presence of trace amounts (z1 % of the total ion current measured at 20 eV) of primary YCf.A set of uncorrected relative ion currents measured at 2445 K is given as an example : Y+, 1.07~ ; YCf, 5.1 x 10-l1 (z3x at 10 eV) ; YC;, 4.00~ ; YC;, 10-l2; YC;, 9.0~ ; YCf, 3.6~6.4~ 10-13 and YC:, 6.7~ The measured ion currents have been related with the corresponding relative partial pressures according to Pi = IiEiT/aiyini. Here the ionization cross sections oi were taken from Mann for Ag, C and Y.Those for the molecular yttrium carbides were taken as the sum of the atomic cross sections, multiplied by an empirical factor of 0.75.12 The multiplier gains Yi were measured for Agf (1.15~lo5), Y+(1.56~ lo5) and YC; (2.37~ lo5). Those for YC;, YCg, YC: and YC,' were taken as the same as those measured for YC;. The isotopic abundance, ni, was taken from Kiser.lo The ratio Ei of the ion current at maximum ion- ization cross section to the observed one at 20 eV was evaluated from the measured ionization efficiency curves as: Ag+, 1.06; Yf,1.10; YC;, 1.12; YC;, 1.0 and YC;, 1.0. For YC; and YC;, it was assumed to be 1.0. RESULTS AND DISCUSSION A summary of the third law enthalpy changes for the pressure independent reactions Y(g) +nC(graPh) = YCn(g> used in the evaluation of the atomization energies of the gaseous yttrium carbides YC, is presented in table 1.The error terms represent standard deviations. The necessary thermodynamic functions were taken from literature for C(graph) and TABLE1.-THIRD-LAW ENTHALPIES OF Y(g)+ nC(graphite) = YC,(g) REACTIONS AND THE DERIVED ATOMIZATION ENERGIES OF GASEOUS YTTRIUM no.of AHt(3rd law) AH,",(MCn)" assumed reactions data sets temp. range/K /lcJ /kJ moi-1 molecular structure y(g)+2C(s) = YCz(g) 28 1824-2530 165.2A3.8 1257f15 Y-C-C Y(g)+3C(s) = YC,(g) 6 2392-2530 328.958.6 1805130 C-Y-C-C Y(P)+4C(S) = YC4(g) 13 2228-2530 314.6k4.1 2530;t24 C-C-Y-C-C Y(g>+Ws) = YCdg) 4 2392-2498 474.8*8.1 3081+35 C-C-Y-C-C-C yk)+6C(s) = yc6(g) 1 2445 483.5 3781 160 C-C-C-Y-C-C-C a Using AHv,o[C(graph)]= 71 1.212.0 kJ mol-1 [ref.(1 3)]. Y(g>.' Those for the gaseous yttrium carbides were calculated by standard methods of statistical thermodynamics on the basis of the assumed linear geometries indicated in table 1. For YC2 and YC4, assumptions similar to those in ref. (1) and (2) were made (C-C distance, 1.31A ; g, = 2, but the Y-C distance was assumed to be 1.82A rather than 2.39A). This bond distance is similar to that estimated for YO (1.79 A)'' and accounts for the bond shortening expected for such a strong bond. The previous estimate of 2.39 A 'corresponds, apparently, to the sum of the simple bond (Rl) radii of Y and C.15 These parameters were also used for the new mole- cules YC3,YC5 and YC6.The free energy functions, (G;-Hg)/IT, in J mol-' K-' (heat content functions, H; -H;, in kJ mol-l) thus obtained for T = 2400 K are : YC2, 309.8 (131.5) ; YC3, 348.9 (178.0) ; YC4, 390.6 (230.2) ; YC5, 436.9 (277.8) and YC6, 470.2 (324.36). The atomization energies, AH&, shown in table 1, were obtained from the measured reaction enthalpies in combination with the heat of sublimation of graphite, K. A. GINGERICH AND R. HAQUE AH:,o = 71 1.2 2.0 kJ rn~l-'.~~The error terms given for the atomization energies are estimated over all the errors. The value for YC2,AH:,o = 1257$-15 kJ mol-', agrees with the literature values of 1229 (1240) 17 kJ mol-1 and 1248 (1259) k21 kJ mol-'.I The value for YC4, AH,",o = 2530f24 kJ mol-l, compares with the corresponding literature value of 2461 (2494) & 18 kJ mol-l.Adjusting the literature values for our choice of the Y-C2 bond distance (adjusted values shown in paren- thesis) results in an improved agreement with our values. The experimental value for D,0,0(YC3)= 1805530 kJ mol-1 is larger than the estimated values 1643 and 1740 kJ rn01-l.~ In analogy to the corresponding uranium carbide^,^ it suggests a Y-C-C-C structure rather than the assumed C-Y-C-C structure. Assumption of a bent structure, as well as of a larger electronic contribu- tion to the free energy function would have theeffect of lowering the experimental value and would thus bring it closer to the predicted ones.The experimental atomization energies of the yttrium carbides, YC, through to YC6, show an alternation of bond energies for each added carbon similar to that observed for the cerium carbide^,^ with the molecules containing an even number of carbon atoms (that is an odd total number of atoms) being more stable. Likewise, the stability of carbon molecules C2-C, alternates, the odd number carbon molecules being more stable. The present investigation of complex yttrium carbides confirms the apparent widespread occurrence of stable transition metal tricarbides and higher polyatomic carbides, e.g., MC5 and MC6. We hope that on the basis of our present results we will also be able to obtain second law data for molecules like MC5 and MC6, in view of our recent extension of the temperature range to = 3000 K.I7 Especially favourable systems appear to be those of lanthanum, cerium and yttrium.Such studies would provide further information as to the most likely geometries and perhaps electronic structure of such polyatomic carbides. We acknowledge the support of the National Science Foundation and the Robert A. Welch Foundation. G. De Maria, M. Guido, L. Malaspina and B. Pesce, J. Chem. Phys., 1965, 43, 4449. F. J. Kohl and C. A. Stearns, J. Chem. Phys., 1969,52,6310. K. A. Gingerich, J. Chem. Phys., 1969,50,2255. K. A. Gingerich, Chem. Phys. Letters, 1978, 59, 136. K. A. Gingerich,D. L. Cocke and J. E. Kingcade, Inorg. Chim. Acta, 1976,17, L1. R. Haque and K. A. Gingerich, to be published.'S. K. Gupta and K. A. Gingerich, to be published. K. A. Gingerich, J. Chem. Phys., 1968, 49, 14. D. L. Cocke and K. A. Gingerich, J. Phys. Chem., 1971,75, 3264. lo R. W. Kiser, Introduction to Mass Spectrometry and its Applications (Prentice-Hall, Englewood Cliffs, N.J., 1965). l1 J. B. Mann, in Recent Developments in Mass Spectrometry, ed. K. Ogata and T. Hayakawa(University Tokyo Press, 1970), pp. 814-819. l2 J. Drowart and P. Goldfinger, Angew. Chem., 1967, 79, 589. l3 R. Hultgren, P. D. Desai, D. T. Hawkins, M. Gleiser, K. K. Kelley and D. D. Wagman, Selected Values of Thermodynamic Properties of Elements (Amer. SOC. Met., Metals Park, Ohio, 1973). l4 K. P. Huber and G. Herzburg, Molecular Spectra and Structure I V. Constants of Diatomic Molecules (Van Nostrand Reinhold, New York, 1979).L. Pauling, The Nature of the Chemical Bond (Cornell University Press, Ithaca, New York, 3rd edn, 1960). l6 H. R. Leider, 0.H. Krikorian and D. A. Young, Carbon, 1973, 11, 555. "S. K. Gupta, R. M. Atkins and K. A. Gingerich, Inorg. Chem., 1978, 17, 3211. (PAPER 9/676)

ISSN:0300-9238    

DOI:10.1039/F29807600101

出版商:RSC    

年代:1980

数据来源: RSC