ISSN:0005-9021    

DOI:10.1002/bbpc.19890930602

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930603

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractA new and versatile photoelectron‐photoion coincidence spectrometer has been developed and advanced to facilitate for the first time the investigation of the valence electronic structure of isolated metal atom clusters up to a mass range of approximately 40000 amu. The neutral cluster distribution, which is synthesized in a doubly skimmed seeded supersonic molecular beam, is probed 130 mm down‐stream by the pulsed and monochromatized output of a newly developed sub‐nanosecond vacuum‐UV/UV‐flashlamp in the photon energy range between 3 and 11.8 eV. Single photoelectrons are energy analyzed and time‐correlated detected either in a field‐free or in a magnetic type time‐of‐flight spectrometer. The corresponding cluster cations are mass analyzed and counted in coincidence in a modified Wiley‐McLaren time‐of‐flight mass spectrometer. The data acquisition electronics is capable of recording and storing simultaneously photoion‐photoelectron coincidence spectra of all those neutral clusters that have sufficient intensity in the molecular beam. First photoelectron spectroscopic results for mass selected mercury clusters up to Hg78are used to discuss the performance of this new technique. — A photoionization mass spectrometry study of sodium cluster beams has revealed shell closings at the sizes being predicted by the cluster shell model. For the case of large mercury clusters a gradual transition from van der Waals type bonding to metallic cohesion occurs in the size range between 20 and 70 atoms. The occurrence of this transition, which has been observed by energy resolved mass spectrometry, is strongly confirmed by photoelectron‐photoion coincidence spectroscopy. Moreover, the photoelectron spectra clearly indicate that the evolution of the valence band structure toward the metallic state is almost fully accomplished for clusters larger than Hg70. The gradually size dependent transition is found to be induced by the rapid increase of the averaged number of nearest neighbours. Hence, the transition can be explained semi‐quantitatively in the framework of

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930604

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractDensity measurements of liquid iodine from the melting curve up to 1000°C and 200 MPa are reported. The measurements have been performed in an internally heated autoclave by a dilatometric method. The results indicate, that liquid iodine remains a normal molecular liquid along its liquid‐vapour coexistence curve. The observed strong curvatures of the isochores at high pressures and high temperatures are consistent with the assumption of a formation of strongly localized charged centers resembling a partial dissociation of iodine into solvated io

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930605

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractMeasurements of the complex dielectric permittivity of water and various concentrated aqueous electrolyte and non‐electrolyte solutions were performed at several frequencies between 5.3 and 18 GHz in dependence of hydrostatic pressure up to 200 MPa at temperatures 5 and 25°C. The dielectric relaxation rate and static permittivity as derived from the experimental spectra show characteristic variations with rising pressure. These are discussed with respect to pressure‐induced changes in molecular motion and spatial arrange

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930606

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractA cationic dye methylene blue (M. B.) was incorporated into polypyrrole (P. P.) films in the course of electrochemical polymerization of pyrrole from aqueous solution containing pyrrole, methylene blue and KCl. The films obtained were blue in color. Absorption bands of M. B. incorporated into P. P. films were broadened compared with those of M. B. in water or in a solution of pyrrole monomer. Methylene Blue incorporated into P. P. films is probably aggregated and is nearly in solid state. Molar absorption coefficient (ϵ) for M. B. incorporated into P.P. films was about half the value of ϵ for M.B. in aqueous solution. The concentration of M.B. incorporated into P.P. films was ca. 0.42—0.49 mol dm−3, while the original concentration of M.B. was ca. 1 mmol dm−3. Methylene Blue was concentrated by a factor of 420–490. The colors of the film changed reversibly to blue by oxidation and to transparent yellow by reduction. The color change was more remarkable than that of P.P. film itself. This is because M.B. was reduced to form leuco M.B. (colorless material) and was reoxidized to form M.B. The response time of color changes between blue and transparent yellow wa

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930607

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractPressure‐composition‐temperature absorption isotherms have been determined for the Pd1‐xREx(RE = Dy, Gd, Sm, and Y;x= 0.05 and 0.08) solid solution face centered cubic alloys in the pressure and temperature ranges 2 ≦P(H2)/mbar ≦ 1000 and 473 ≦T/K≦ 873 using the manometric method. The partial molar enthalpy of solution of hydrogen at infinite dilution (ΔH̄0H) becomes more exothermic with increasing content of RE. The partial molar excess entropy of hydrogen solution at infinite dilution (ΔS̄E.0H) decreases with xRE. A correlation of the atomic diameter (dRE) of the substituting rare‐earth metals when in solution in palladium with ΔH̄0Hand with the metal‐hydrogen interaction shows that the increase in the exothermicity of the Pd1‐xRExsolid solution alloys is due to the lattice expansion and an attractive metal‐hydrogen interaction. From the correlation of ΔH̄0HwithdREof Pd1‐xREx(x= 0.05 and 0.075), ΔH̄0Hof Pd1‐xREx(RE = Yb, Ho, and Eu;x= 0.05 and 0.075) solid solution alloys have been predicted. The dependence of ΔH̄0Hof the “expanded” and “contracted” Pd1‐xMxalloys on the size of the octahedral interstitial hole sit

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930608

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractThe temperature dependence of1H NMR second moments and spin‐lattice relaxation times,T1andT1ϱin the laboratory and rotating frames, respectively, were observed for solid methylguanidinium (MeguH+), 1,1‐dimethylguanidinium (1,1‐Me2guH+), 1,2,3‐trimethylguanidinium (1,2,3‐Me3guH+), and 1,1,3,3‐tetramethylguanidinium (1,1,3,3‐Me4guH+) chlorides. Phase transitions were found for (1,1‐Me2guH)Cl and (1,2,3‐Me3guH)Cl at 400 and 409 K, respectively, which were confirmed by differential thermal analysis experiments. Below room temperature, rapid C3reorientational motions of CH3groups were detected for the all cations in the above crystals. The activation energy for the motion of each CH3group in the cations was evaluated. Above room temperature, the temperature dependences ofT1ϱwere determined againstT−1for (1,1‐Me2guH)Cl, (1,1,3,3‐Me4guH)Cl, and their partially deuterated (NH2→ ND2) analogs. For these salts,1HT1ρ minima were observed and could be interpreted as arising from the 180° flip motions of the NMe2group and also of the whole cation for (1,1‐Me2guH)Cl and its deuterated analog about the C+—NMe2axis of the cations, and the whole cationic 180° flip motion about the C+—NH2or C+—ND2bond axis of the cation for (1,1,3,3‐Me4guH)Cl or its deuterated analog, respectively,

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930609

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractMolecules of copper phthalocyanine substituted with four 18‐crown‐6 moieties, were aggregated with the help of K+, Rb+, and Cs+picrates. Possible structures were proposed based on computer analysis of X‐ray powder diffraction patterns: for the crowned phthalocyanine an orthorhombic cell with:a= 50.77,b= 25,c= 8.7 Å. For its metal picrate complexes, tetragonal structures were found:a=b= 22.76,c= 12.99 Å (K+‐complex);a=b= 29.44,c= 10.63 Å (Cs+‐complex);a=b= 29.44,c= 10.40 Å (Rb+‐complex). A.c. impedance spectroscopy showed an increase in the electronic conductivity of 2 to 3 powers of ten, if crowned phthalocyanine was aggregated by means of a metal picrate salt. In the K+complex only electronic conductivity could be detected. The Rb+and Cs+complexes exhibited cation condu

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930610

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractThe phase behaviour and thermotropic and barotropic phase transitions of different model biomembranes (DPPC, DMPC, DEPC and POPC*)), which consist of different hydrocarbon chain length and degree of unsaturation, have been investigated by small‐angle neutron scattering (SANS) as a function of temperature and pressure up to about 65°C and 3 kbar, respectively. A pressure induced structural phase transition from a liquid‐crystalline to a gel state is observed for the whole temperature range studied. The pressure of this transition increases with increasing temperature with a slope dTm/dPof about 21°C/kbar, which is common for all the different lipids investigated. The SANS experiments indicate that the effect of the two trans double bonds in DEPC and the cis double bond in the sn‐2 hydrocarbon chain of POPC enhances the conformational disorder in the hydrocarbon chains not only in the liquid‐crystalline, but also in the gel state. For DEPC and POPC the prefered structural conformation in the gel state is probably not tilted as it is in the gel state of the saturated phospholipids DMPC and DPPC. Only for DPPC multilamellar vesicles, an additional gel phase at higher pressures has been observed, which can be ascribed to an interdigitation of the hydrocarbon chains of opposing chains in the lipid bilay

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930611

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY