摘要:

AbstractRaman spectra of polymeric photoconductive copper organoacetylides (RCCCu)xdiffer substantially from the spectra of other CuIor AgIcompounds which lack photoconductive properties. Also, there is a significant redistribution of band intensities in the Raman spectra of the copper organoacetylides compared with the spectra of the parent acetylenes. The triple bond stretching vibration,v(CC), atca1950−1900 cm−1,v(C‐C) atca950−700 cm−1and the lines atca600−500 cm−1, caused by deformations of angles between the multiple and single bonds, in the spectra of copper acetylide exhibit an increase in intensity by a factor of 10–100 compared with the spectra of parent acetylenes RCCH. The vibrational bands characteristic of the R substituent itself seem to be very weak in comparison with the unusually strong band of the acetylide in the lower Raman shift range. The origin of these unusual Raman intensities in copper organo

ISSN:0377-0486    

DOI:10.1002/jrs.1250260602

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractAn empirical correlation is developed for relating the wavenumbers of (WO) stretching modes to WO bond lengths and bond strengths for tungsten oxide reference compounds. A least‐squares exponential fit of crystallographically determined WO bond lengths to the wavenumbers of their Raman stretching modes is presented along with a relation between WO bond strengths, in valence units, and wavenumbers of Raman stretching modes. The empirical bond length/stretching mode wavenumber/bond strength relationships lead to a unique and effective method of interpreting Raman spectra of tungstate species. This method leads to the WO bond lengths and coordination of the tungstate species. The utility of the method is illustrated by estimating the wavenumbers of the Raman stretching modes for the ideal WO4tetrahedron and WO6octahedron, and the bonds lengths and coordinations of the tungstate species in the reference compounds Na2WO4, PbWO4, CaWO4and Bi2WO6. In addition, the WO bond lengths of the WO6octahedra in crystalline Ba2MgWO6are reported for the first time. This new approach for evaluating the Raman spectra of tungstate species is expected to be generally applicable to all tungstates, regardless of environment, physical state, or ox

ISSN:0377-0486    

DOI:10.1002/jrs.1250260603

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe Bi2O3‐WO3system was examined using Raman spectroscopy. The Raman spectra of bismuth tungstate samples having Bi: W ratios of 2:1, 4:1 and 14:1 were used to identify the bismuth tungstate phases present at these compositions. The bismuth tungstate phases which occur were found to depend on the Bi: W ratio. The 2:1 composition consists of only the Bi2WO6phase and the 14:1 composition consists almost entirely of the sillenite phase. The 4:1 composition, however, is multi‐phase and consists of Bi2WO6, the sillenite phase, and another phase referred to as 7Bi2O3‐2WO3. The Raman spectra were used to determine the coordination of the tungstate species as well as their WO bond lengths in each of these

ISSN:0377-0486    

DOI:10.1002/jrs.1250260604

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe Raman (3100—10 cm−1) and infrared (3100—40 cm−1) spectra of methylvinyldifluorosilane, CH2CHSiF2CH3, were recorded for the gas and solid. Additionally, the Raman spectrum of the liquid was recorded and qualitative depolarization values were obtained. The observed bands in the fluid states are assigned on the basis of the more stablegauche(antiperiplanar) conformer where one of the fluorine atoms is eclipsing the double bond and the less stablecis(synplanar) conformer. However, in the annealed crystalline solid, only thecisconformer remains. A complete vibrational assignment is proposed for both conformers based on infrared band contours, Raman depolarization data, group wavenumbers and normal coordinate calculations. The experimental stability, barriers to internal rotation, and fundamental vibrational wavenumbers are compared with those obtained from theab initiocalculations employing the RHF/3‐21G*, RHF/6‐31G*and MP2/6‐31G*basis sets and to the corresponding quantities obtained for some simi

ISSN:0377-0486    

DOI:10.1002/jrs.1250260605

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractA series of polyethylene samples were analysed using a micro Raman system. The data were analysed using a commercial partial least‐squares package and correlated with the polymer density. A correlation coefficient of up to 0.98 was obtained, depending on the spectral region used. A standard error of prediction of 2.15 kg m−3was obtained and the densities of ‘blind’ samples were predicted with good a

ISSN:0377-0486    

DOI:10.1002/jrs.1250260606

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe groove binding dye Hoechst 33258 was investigated both in aqueous solution and in the adsorbed form on silver colloids and island films. Fourier transform Raman, resonance Raman and surface enhanced resonance Raman spectra were used together with the results of a normal coordinate analysis for a comprehensive assignment of the rich vibrational spectrum. Relative band intensities in the SERRS spectra indicate that the molecule is adsorbed with its long axis oriented along the silver surface and with the planes of the benzimidazole rings approximately parallel to the surface. The molecule is bound to the surface as a cation protonated at a piperazine nitrogen atom and is desorbed on complete deprotonation.

ISSN:0377-0486    

DOI:10.1002/jrs.1250260607

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractPolarization‐sensitive coherent Stokes Raman scattering (CSRS) measurements of oxy‐ and deoxyhaemoglobin in aqueous solutions are reported. The excitation wavelengths used were chosen in the region of theQabsorption bands to achieve twofold electronic resonance. The dispersion profiles of all independent susceptibility χ(3)components and purely anisotropic and anti‐symmetric scattering contributions were resolved within the frequency non‐degenerate CSRS scheme. Eight bands of oxyhaemoglobin and five bands of deoxyhaemoglobin were observed in the range 1500‐1680 cm−1. Simultaneously fitting sets of polarization spectra provided vibrational parameters (positions, bandwidths, amplitudes, phases and CSRS depolarization ratios) for each compound. Major bands were assigned to the non‐totally symmetricv10,v11andv19modes of the porphyrin macrocycle. The phases calculated exhibited a correlation with the symmetry of the vibrations. On the basis of the spectral fits, the three additional peaks arising in the oxyhaemoglobin spectra could be ascribed to the bands of intermediate deoxyhaemoglobin. The occurrence is due to the partial photolysis of oxyhaemoglobin. Vibrational parameters of these bands were found to be essentially similar to the parameters of the bands observed in the spectra of the stable deoxyhaemoglobin. Despite the asymmetric character predicted, the major bands were all contributed to by a considerable isotropic component. A decrease in the depolarization ratio P 1212Rof the anomalously polarizedv19mode from 7.7 in oxyhaemoglobin to 4.3 in deoxyhaemoglobin was observed. Such a decrease in anti‐symmetric character of the vibration on release of the ligand supports the occurrence of deformation of th

ISSN:0377-0486    

DOI:10.1002/jrs.1250260608

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractPressure‐induced phase changes in SrMoO4were investigated by high‐pressure Raman spectroscopy in a diamond anvil cell. The scheelite‐type SrMoO4transforms in to a monoclinic lattice near 13 GPa and retains this structure up to 37 GPa, the limit of pressure tested. There is no pressure‐induced amorphization in this simple molybdate up to this pressure, as in the case of structurally complex molybdate systems. The optical absorption characteristics of SrMoO4change considerably with pressure, the sample turning progressively deep orange‐brown with increase in pressure. This change is connected with the lowering of the d‐state of molybdenum in the MoO4ion with increase

ISSN:0377-0486    

DOI:10.1002/jrs.1250260609

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractDephasing of vibrations of all‐trans‐β‐carotene in cyclohexane was studied by resonance CARS in the wavenumber domain, using scanning CARS, and also in the time domain, by interferometric CARS (I‐CARS) applying temporally incoherent light from non‐transform limited broadband lasers. The ground‐state vibrations (1002, 1153, 1188, 1210 and 1522 cm−1) are predominantly homogeneously broadened and have dephasing times ranging from 0.6 to 0.7 ps. For broadband wavenumbers in the long‐wavelength wing of the absorption band and a Stokes laser intensity exceeding 0.5 GW cm−2, the CARS signal saturates and decreases above 1 GW cm−2. The decrease in the CARS signal is accompanied by the appearance of additional Raman lines. Taking into account all these Raman lines (solvent lines and two additional very broad lines), the features of the I‐CARS can be explained with the same parameters as for scanning CARS. Consideration of these additional lines is essential. Using excitation wavenumbers within the absorption band, power broadening of the 1522 cm−1line is observed. In some experiments, diffraction by a laser‐induced grating str

ISSN:0377-0486    

DOI:10.1002/jrs.1250260610

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractNear‐infrared Fourier transform Raman spectra (3400 to — 20 cm−1) for the solid phases of indigo, thioindigo, selenoindigo andN,N'‐dimethylindigo were recorded with excitation using Nd:YAG laser radiation at 1064 nm. A complete vibrational assignment is proposed supported by the results ofab initiocalculations. The spectra are complementary to the IR spectra recorded earlier. They also complete earlier results of resonance Raman spectroscopy. The spectra support a molecular structure of the indigo chromophore with a cross‐conjugated vinylogue ami

ISSN:0377-0486    

DOI:10.1002/jrs.1250260611

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY