摘要:

AbstractThe CO stretching Raman bands of dimethylformamide and acetone have been studied for the pure liquids and for solutions of alkali metal halides and perchlorates in these liquids. An enormous reduction in the intensity of these bands was found in the presence of the perchlorate ions, especially in the case of dimethylformamide. In each case a new band appears in the CI–O stretching region of the perchlorate. The results indicate the formation of stable complexes between the organic molecule and perchlorate ion through the CO

ISSN:0377-0486    

DOI:10.1002/jrs.1250160602

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe results of an experimental and theoretical study of the resonant secondary emission spectra at 4.2 K of wide gap ionic insulators (lattice of the NaCl type) are presented. The well developed character of the free exciton luminescence and the multiphonon resonant Raman scattering spectra (which contain mainly LO lines) point to Frölich intraband scattering of free excitons (polaritons) on LO phonons. It is established that the ratio of the scattered line intensities of the first and second order has a square dependence on the scattered polariton wave vector. For the spectral range 4.97–3.30 eV the dispersion of the scattering cross‐section with participation of LO(Γ) phonous has been measured for the first time. A resonant enhancement of the multiphonon scattering line intensities on the LO(Γ), LO(X) and TO(Γ) phonons has been observed. Calculation of the dispersion of the scattering cross‐section has been performed using a theoretical model taking into account the scattering of hydrogen‐like excitons on LO phonons. Analysis of the cross‐section leads to the conclusion that in the excitation frequency range ω>Eg‐4Rthe main contribution to σ(ω) comes from the discrete excitonic states, but for ωEg‐4Rthe states of the electron‐hole continuum play the main role. Agreement between theory and experiment has been achieved by taking into account the electronic damping. The influence of the excitation intensity on the structure of resonant Raman scattering spectra in LiH cry

ISSN:0377-0486    

DOI:10.1002/jrs.1250160603

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractDesign features of a computer controlled, diode array detector equipped spectrometer for the acquisition of Raman optical activity (ROA) data are presented. This instrument utilizes an artifact reducing dual lens light collection system, and a novel approach to synchronize the light modulation and the detection electronics. ROA spectra, collected at full optical apertures, and without a polarization analyzer in the scattered light, are reported and compared to depolarized published data.

ISSN:0377-0486    

DOI:10.1002/jrs.1250160604

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe conformation of low‐salt LiDNA in fibrous form has been studied by Raman microspectroscopy. The recorded spectrum of a fibre soaked in ethanol is very similar to that of a fibre at low relative humidity. From x‐ray experiments it is known that in the latter case the DNA adopts theCconformation. Therefore, it can be concluded that this is also the case in a low‐salt LiDNA fibre soaked in ethanol. Further, it has been observed that the DNA conformation did not change when the excess ethanol was allowed to evaporate. TheCform is also found when the fibre is in contact with ethanol vapour only. These results are in agreement with x‐ray studies. However, our experiments with a LiDNA fibre intert‐butanol are not in agreement with x‐ray results. Only when thetert‐butanol is absolutely free from water is a state intermediate between the B and

ISSN:0377-0486    

DOI:10.1002/jrs.1250160605

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractA band shape function for the isotropic Raman scattering described in terms of the band width in the weak coupling limit and the relaxation time of the bath mode has been proposed by summing the results of Berneet al. [J. Chem. Phys.45, 1086 (1966)], Wang [Mol. Phys.33, 207 (1977)] and Knauss [Mol. Phys.36, 413 (1978)]. The results of band analyses with this function have been compared with those obtained from other conventionally used band shape and correlation functions. The present function is preferable for precise interpretation of vibrational relaxation mechanisms, particularly for those cases where temperature and concentration dependence of the band parameters are involved.

ISSN:0377-0486    

DOI:10.1002/jrs.1250160606

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractRaman scattering is treated using the displaced harmonic oscillator model. The time‐dependent approach to the Raman scattering tensor was adopted and the exact propagation of gaussians on harmonic surfaces was exploited. An insight into the effect of the damping constant on the Raman excitation profiles was thus obtained. It is shown that the dynamics of the wavepacket propagation on the excited state surface governs the difference between continuum resonance Raman scattering and discrete resonance Raman scatterin

ISSN:0377-0486    

DOI:10.1002/jrs.1250160607

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe hyper Rayleigh and hyper Raman (0–1600 cm−1wavenumber shift) spectra of oriented single crystals of ammonium chloride and ammonium bromide are reported. It is demonstrated that hyper Rayleigh scattering is a very sensitive measure of the presence of a centre of symmetry within a crystal structure and this property is used to investigate the residual ordering within an ammonium chloride crystal at 55 K above the order‐disorder phase transition. The hyper Raman wavenumber shifts associated with the transverse (TO) and longitudinal (LO) components of the optic mode, the librational mode which is infrared and Raman inactive, and the H–N–H internal mode were observed for both crystals. A basis for the interpretation of the relative hyper Raman intensities of the LO and TO modes is provided by an extension of the Poulet treatment of the relative intensities in the Raman

ISSN:0377-0486    

DOI:10.1002/jrs.1250160608

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractRaman scattering from CsD2PO4was observed in the paraelectric and ferroelectric phases. The line width and the frequency of one of the totally symmetricAmodes were measured as a function of temperature. An anomalous change in the line width was observed and this is qualitatively discussed in relation to the frequency shift below the transition temperature.

ISSN:0377-0486    

DOI:10.1002/jrs.1250160609

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractRaman and infrared spectra (10–5000 cm−1) of single crystals and polycrystalline samples of CH3NH3NO3and of its ND3deuterated derivative were investigated in the temperature range 30–400 K. A systematic temperature dependence study of the frequencies and band widths was performed. The results show the existence of three phases. Assignments of most of the bands observed are proposed. Raman spectra of single crystal CH3NH3NO3in the internal and lattice region are interpreted based on aD2h16structure and relative polarization data. A thermal hysteresis characteristic of the first order was observed in the phase II⇌phase I transition. Raman and infrared spectral features of phase I indicate this to be a plastic phase, in which cations and anions exhibit isotropic reorientational motion. The spectral changes that occur in the phase II → phase III transition suggest freezing out of thermal motion and reveal only minor structural changes in phase III compared with

ISSN:0377-0486    

DOI:10.1002/jrs.1250160610

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe Raman spectrum of I4O9, formed by the gas‐phase reaction of I2with O3, has been measured. Freshly prepared samples of I4O9gave broad band spectra characteristic of an amorphous solid. Vibration bands at 780, 740, 620 and 450 cm−1were observed. It was established conclusively that I4O9is a distinct molecular species and not a mixture of I2O5and I

ISSN:0377-0486    

DOI:10.1002/jrs.1250160611

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY