摘要:

AbstractA theory for Raman band shapes is developed by using the stochastic model. The correlation between electronic and vibrational dephasing is taken into account explicitly. Raman bands become significantly asymmetric in the case of a strong correlation. The Raman band shape can therefore be used to estimate the extent of correlation between the electronic and vibrational dephasing processes. The fact that Raman bands are usually Lorentzian means that the two dephasing processes are not strongly correlated in many cases. The microscopic aspect of the dephasing processes is discussed.

ISSN:0377-0486    

DOI:10.1002/jrs.1250221102

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe pressure‐broadening coefficients for the self‐broadened S0(0), S0(1) and S0(2) pure rotational Raman lines of hydrogen and the S0(0) to S0(4) lines of deuterium were determined experimentally over the pressure range 1–100 bar and the temperature range 90–375 K. Broadening coefficients were also determined for the same lines in hydrogen and deuterium perturbed by helium, argon, oxygen, nitrogen, carbon monoxide and hydrogen chloride over the pressure range 2–100 bar, with a partial pressure of the host gas of 1 bar and a temperature of 293 K. In addition, the S0(0) pure rotational line of deuterium broadened by carbon monoxide and nitrogen was studied over the same pressure range and a temperature range of 100–293 K. The results are discussed and compared with those of previous studies in the

ISSN:0377-0486    

DOI:10.1002/jrs.1250221103

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractRaman spectra of the α‐, β‐, γ‐ and smectic polymorphs of isotactic polypropylene were recorded at 298 and 16.5 K. At 298 K the spectra of the polymorphs were very similar except in the antisymmetric CH stretching region. However, at 16 K the Raman spectra of the polymorphs show different features in several wavenumber shift regions. Comparisons are made with infrared spectra recorded at 298 and 100 K and interpretations are made on the basis of non‐equivalent sites in the monoclini

ISSN:0377-0486    

DOI:10.1002/jrs.1250221104

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractA general method is presented for determining the shape and orientation of the Raman tensor of a molecule in a uniaxial crystal using a Raman microscope. First, equations are derived to connect the Raman tensor components (αxx, αyy, etc.) of a molecule to the Raman tensor components (αaa, αcc, etc.) of a crystal that is composed of molecules in a uniaxial arrangement, with an orientation specified by the two angles χ and θ. Next, a method is presented to obtain a correct set of values of the intensity ratiosIac/IaaandIcc/Iaafrom observed values of the intensity ratios measured with a Raman microscope. To augment the experimental data, the depolarization ratio ρ (for a completely random molecular orientation) is plotted as a function ofr1= αxx/αzzandr2= αyy/αzz, so that a possible set ofr1andr2values can be found from an observed value of ρ. The method has been applied to an aspartame IIA crystal (P41). A set of values ofr1,r2, χ and θ has been determined for each of the following Raman fundamentals: 1741 cm−1(ester CO stretch), 1667 cm−1(amide I), 1275 cm−1(amide III) and 1204 cm−1(CCphenylstre

ISSN:0377-0486    

DOI:10.1002/jrs.1250221105

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractSolid polybromide‐containing functional polymers were obtained from basic anion‐exchange resins. The chloride or hydroxide anions of the commercial resins were exchanged by bromide, then dried under anaerobic conditions and allowed to react with a gaseous bromine phase. The formation of linear, slightly asymmetric tribromides was proved by Raman and far‐IR spectroscopy. The tribromide spectra are characterized by the symmetrical stretching vibration ν1at about 160 cm−1and the antisymmetric stretching vibration ν3at about 200 cm−1. If the Br2: Br−molar ratio is greater than 1 an additional band could be observed at about 255 cm−1. This band is assigned to the stretching vibration of coordinated bromine. It is shifted in the direction of free bromine at about 300 cm−1with increasing bromine content in the functional polymers. According to the spectroscopic results, the anion structure in amorphous polybromide‐containing functional polymers can be explained by tribromide ions and bromine molecules interacting with the tribromide. The thermal instability of higher polybromides was also prove

ISSN:0377-0486    

DOI:10.1002/jrs.1250221106

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractRaman and infrared spectra of solid dichlorofluoromethane were recorded in both the internal and lattice mode regions at 20 and 80 K. The lattice spectra are consistent with a non‐centrosymmetric unit cell containing at least four molecules. All nine internal modes are observed, and their multiple components are interpreted in terms of crystal field effects and isotopic splitting

ISSN:0377-0486    

DOI:10.1002/jrs.1250221107

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThin sputtered films of the high‐Tcmaterial YBa2Cu3O7‐Δwere investigated using 180° back‐scattering geometry with Fourier transform (FT) Raman spectroscopy. It is established that the main bands in the spectra of a YBa2Cu3O7‐Δfilm on strontium titanate substrate exhibit similarity with those obtained for oriented untwinned crystallites of the superconductor having theirc‐axis perpendicular to the surface of the substrate. No degradation or excessive heating of the film was observed with 1.064 μm excitation for low laser powers. The film on a magnesium oxide substrate gives unique evidence of the isolated strong, featureless, almost flat continuum, producing a broad maximum near the region of the antiphase axial bending O(2)Cu(2)O(3) motions of planar oxygens at very low excitation energy. This appears to be the first application of FT‐Raman spectroscopy using near‐infrared excitation (1.064 μm) to the field of high‐temperature superconducting films and their d

ISSN:0377-0486    

DOI:10.1002/jrs.1250221108

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractCorrelations are established between the structural data provided by x‐ray diffraction and Raman spectroscopy on borate crystals. A linear relationship is found to be adequate to describe the bond length‐stretching frequency correlations in nine meta‐, pyro‐ and ortho‐borate crystals consisting solely of triangular borate arrangements. This result allows bond length and strength predictions for newly synthesized compounds to be made, as well as assisting in the elucidation of the influence of borate tetrahedra on the πp bonding of BO−‘probes’ in borate crystals. A wide field of applications in the structural study of borate gla

ISSN:0377-0486    

DOI:10.1002/jrs.1250221109

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe dissociation constants for an acetonitrile‐zinc complex, (CH3CN)Zn2+, were measured in aqueous solutions containing zinc salts (40‐80%, w/w) and acetonitrile by Raman spectroscopy. Quantitative measurements of the intensity of the free and complexed ν(CN) Raman bands at 2264 and 2320 cm−1, respectively, were used to determine the average enthalpy and entropy of the complex dissociation to free acetonitrile in the temperature range 293‐343 K for a 70% (w/w) solution of zinc chloride (0.052 mol) in an aqueous solution containing acetonitrile (0.024 mol); δH° and δS° values of 8.4 ± 0.5 kJ mol−1, respectively,

ISSN:0377-0486    

DOI:10.1002/jrs.1250221110

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractComplete polarized Raman spectra in the region of OD stretchings in a partially deuterated Rochelle salt were observed at room temperature and 77 K. The spectra were analysed by comparison with calculated intensity variations, identifying some bands definitely and deducing a ferroelectric dipole with a two‐site structure, where the OD stretchings are 2520 and 2424 cm−1at room temperature. The infrared spectra in the region of OD stretchings and also OH decoupled stretchings were observed in the temperature range 310‐20 K. One of two components in the ferroelectric dipole at 2507 cm−1was observed even at 20 K, indicating a small energy difference between the two sites. On the other hand, no important spectral change at 2507 cm−1was found on passing through the ferroelectric phase transition. An OH group with a two‐site structure with an energy difference of 2.4 kJ mol−1was observed for the first time at 3536 and 3523 cm−1at 240 K, although the corresponding OD stretching was not split. It is considered that this group is not respo

ISSN:0377-0486    

DOI:10.1002/jrs.1250221111

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY