摘要:

AbstractThe theory of the hyper‐Raman effect in molecular gases is reviewed. In order to calculate relative intensities of vibration‐rotation lines in hyper‐Raman spectra, line strengths are introduced and these are calculated using the method of irreducible spherical tensors. It transpires that the hyper‐Raman effect caused by scattering of a quasi‐monochromatic light beam can be fully described by five independent line strength expressions. Rotational and vibrational selection rules as well as depolarization ratios for linearly, circularly and naturally polarized incident light are derived and discussed. The angular dependence of the scattered intensity is also given in the form of polar diagrams. To some extent the paper presented here parallels that published by Placzek and Teller54in 1933 on the rotational structure of vibrational bands in conventional Raman spectra caused by a spontaneous two‐photon scatter

ISSN:0377-0486    

DOI:10.1002/jrs.1250120102

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe Raman spectra of sixteen compounds derived from HN(SO3)22−have been compared. The results show that the substitution of one or more of the oxygens of the original tetrahedron SO42−by a ligand F, Cl, NH, N, implies a contraction of the free SO bonds. This is characterized by the shifting of the symmetrical stretching frequency νs(SO). The polarizing power of the associated cations can also

ISSN:0377-0486    

DOI:10.1002/jrs.1250120103

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY

摘要:

AbstractLinewidths of isotropic and anisotropic Raman bands of the CD stretching mode of chloroform‐dhave been measured in ether and in carbon tetrachloride, and the hydrogen bonding between chloroform and ether has been investigated from the analysis of the linewidths. Theoretical Raman linewidths due to vibrational and reorientational relaxation have been calculated for two models. One is a non‐hydrogen‐bonded model where a single chloroform molecule is surrounded by ether molecules without forming hydrogen bonds, and the other is a hydrogen‐bonded model where a chloroform‐ether complex as a solute is surrounded by ether molecules. The concentration dependences of experimental Raman linewidths are discussed in relation to these

ISSN:0377-0486    

DOI:10.1002/jrs.1250120104

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY

摘要:

AbstractRaman scattering from single crystals of ammonium sulphamate have been recorded in the region 30–3400 cm−1with He‐Cd laser excitation. The libratory and translatory modes observed in all the six polarizations were assigned. The assignment of internal modes of ammonium ion indicates minimum distortion of the ion from the tetrahedral symmetry. The presence of medium hydrogen bonding and the range of correlation field splitting are disc

ISSN:0377-0486    

DOI:10.1002/jrs.1250120105

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe resonance Raman spectra of 9,9′‐bifluorenylidene have been measured in the 450–510 nm region either in solution or in the solid state by using six lines of the Ar+laser. The analysis of the excitation profiles allowed inferences to be drawn concerning the vibronic structure of the lowest electronic excited state. The different behaviour shown by the profiles relative to the solid and the solution has been interpreted as due to different Franck‐Condon overlap integrals between the ground and the excited electronic states. A vibrational assignment of the g modes is proposed on the basis of a polarized Raman spectrum in solution taken with the 632.8 nm line of a He‐Ne laser. Electronic spectra of NaCl pellets and of oriented polycrystalline samples were also

ISSN:0377-0486    

DOI:10.1002/jrs.1250120106

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe infrared and Raman spectra of methylviologen (1,1′‐dimethyl‐4,4′‐bipyridine dication, MV2+) have been measured from both the solid dichloride and aqueous solutions. The preresonance behaviour of MV2+Raman bands showed that the absorption at ˜196 nm is mainly responsible for the resonance scattering process in MV2+. In the region below 1700 cm−1, nine polarized (p˜1/3) resonance Raman bands of the methylviologen radical cation, MV+, were assigned to in‐plane ring modes. Arguments are given that the chromophore of MV+may also partially include the methyl groups. The excitation profiles of the MV+fundamentals, measured with laser wavelengths covering the range 350.6–676.4 nm, reveal three main groups of modes, each behaving differently for the excitation in this range. Modes containing largely ν(CC) ring contributions are mainly coupled with electronic transitions at ˜395, ˜605 and ˜720 nm and yield simple excitation profiles. Modes involving principally the vibrations of the N+CH3group show complicated interference peaks in the whole range of the excitation profiles. γ(CCC) is mainly coupled with the absorption at ˜620 nm. Resonance Raman bands of the (MV+)2dimer have been characterized through studies of the concentratio

ISSN:0377-0486    

DOI:10.1002/jrs.1250120107

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe Raman spectrum of the very weak 2ν4band of CH4has been recorded in the region 2460–2675 cm−1with a spectral resolution of about 0.30 cm−1and with two different orientations of the linearly polarized exciting light relative to the direction of observation. The two exposures are used to obtain the purely isotropic and the purely anisotropic Raman spectrum of the band. The two spectra are interpreted in terms of a model which takes explicitly into account vibrational and rotation‐vibrational interactions with other vibrational states. Using molecular constants determined primarily from infrared spectroscopy, theoretical contours are calculated which agree very satisfactorily with the experimental ones. For the isotropic spectrum it is found that two different values of the ratio between the 2ν4(A1) and the ν1transition moment matrix elements reproduce the spectrum equally well. It is shown that the major part of the intensity in the isotropic and anisotropic Raman spectrum is borrowed from the ν1(A1) and the ν3(F2) fundamentals, respectively, through Fermi‐type interactions, and it is also shown that the 2ν4isotropic Raman band would have been 4–6 times more intense, if the 2ν4(A1) transition moment matrix element h

ISSN:0377-0486    

DOI:10.1002/jrs.1250120108

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY

摘要:

AbstractRaman spectra of single crystals of iodoform have been investigated over the temperature range 10–300 K and under hydrostatic pressure up to 14 kbar. The pressure‐induced shifts in vibrational frequency of many different modes have been used to calculate their respective Gruneisen parameters γ which are found to vary both with the frequency and pressure. They are much greater for the intermolecular modes than for the internal modes. The infrared absorption spectra have also been observed at different temperatures and are used together with the Raman data to obtain dν/dTfor each band. Some new infrared assignments are sugg

ISSN:0377-0486    

DOI:10.1002/jrs.1250120109

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY

摘要:

AbstractAmorphous V2O5can be obtained by cooling from the melt. This amorphous oxide is very sensitive to water vapour and can even be dissolved in water to give a vanadium pentoxide gel. The hydration process has been followed by infrared and Raman spectroscopy between 20 and 4000 cm−1. Short‐range order in the amorphous oxide appears to be almost the same as in orthorhombic V2O5. The amorphous phase could even be described as made of small crystallites about 100 Å in diameter. The structure of amorphous V2O5does not seem to be modified by water adsorption, at least during the first stages of the hydration process. However, a drastic modification occurs when enough water is added to give a gel. A general shift to lower frequencies is observed, indicating a weakening of the VO bonds, presumably associated with the formation of new VOH2bonds. Two different water species have been identified, one of which seems to be almost free of hydrogen bonding. Short‐range order in the gels seems to be quite well defined and the spectra could be interpreted either in terms of crystallites, as in amorphous V2O5, or in terms of molecular (or macromolecular) species containing V2O5, (H2

ISSN:0377-0486    

DOI:10.1002/jrs.1250120110

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY

摘要:

AbstractMolecular vibrational and reorientational relaxation studies on CH2Br2are presented using Raman band contours of ν3(CBr symmetric stretch) and ν4(BrCBr symmetric bend) bands. Fourier transforms of isotropic and anisotropic parts of the bands were employed to obtain correlation functions and correlation times. The results are compared with those reported previously and discussed in the light of the existing t

ISSN:0377-0486    

DOI:10.1002/jrs.1250120111

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY