摘要:

AbstractGlassy, heterocyclic copolymers of an epoxy oligomer and hexamethylene diisocyanate were characterized by low‐frequency Raman scattering spectra at room temperature. The experimental data were treated according to the formalism of the theory of inelastic light scattering from fractons to derive structural information in the scale range below 10 nm. The samples studied were shown to behave essentially fractal‐like in the range of characteristic scales (on an order‐of‐magnitude basis) spanning roughly the chain persistence length (ca.0.7 nm) as a lower structural limit and the network mesh size (ca.3 nm) as an upper structura

ISSN:0377-0486    

DOI:10.1002/jrs.1250250202

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractCARS spectra of the ν1band of water vapour at room temperature and 2100 K over a large pressure range (200–19 × 105Pa) were studied experimentally and theoretically. The influence of N2and H2O on the rotational relaxation processes of H2O in H2ON2mixtures was investigated. Modelling of the CARS spectrum was performed using the relaxation matrix inversion procedure. Two rotational relaxation models based on energy and angular momentum transfer were tested and good agreement between experiment and theory was found for all the conditions studied. At 19 × 105Pa and 2100 K, motional narrowing was found to be weak, allowing calculation of the CARS spectrum with the simple isolated‐li

ISSN:0377-0486    

DOI:10.1002/jrs.1250250203

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe relative SERS (surface‐enhanced Raman scattering) enhancement factors for pyridine adsorbed on a silver electrode were determined as a function of the laser wavelength and applied potential. The charge‐transfer (CT) effect on Raman intensity,GCT, was determined by analysing the relative Raman intensity as a function of the potential, taking into account voltage‐dependent coverage of the silver electrode. The total chemical effect was defined as a product ofGCTand the so‐called ‘active‐sites’ effect and was estimated as equa

ISSN:0377-0486    

DOI:10.1002/jrs.1250250204

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe Raman (3200–10 cm−1) and infrared (3200–30 cm−1) spectra were recorded for gaseous and solid phases of ethyldichlorosilane, CH3CH2SiHCl2. Additionally, the Raman spectrum of the liquid was recorded and quantitative depolarization values were obtained. In the spectra of the gas and liquid, both thetransandgaucheconformers are present with thegaucheconformer being the dominant rotamer at ambient temperature, but at −126°C thetransconformer dominates the spectrum. Only thetransform is present in the vibrational spectrum of the solid. In the Raman spectrum of the liquid at ambient temperature, the amount of thegaucheconformer is significantly reduced compared with that present in the gas. From the relative intensities of two pairs of Raman lines of the liquid at 192/180 and 661/709 cm−1as a function of temperature, the enthalpy difference is found to be 143 ± 17 cm−1(408 ± 48 cal mol−1) with thetransrotamer the more stable conformer. Similar variable‐temperature studies of the infrared spectrum with the sample dissolved in liquid krypton were carried out and the value of the enthalpy difference was determined to be 61 ± 10 cm−1(172 ± 30 cal mol−1). This value should be near the ΔHvalue for the Gas. The asymmetric torsion is observed at 71 cm−1for thegaucheconformer and the potential function governing the conformational interchange is estimated. The fundamenal modes of both conformers were assigned utilizing band contours, depolarization values, group frequencies and normal coordinate calculations. The SiH bond distance was determined to have values of 1.475 and 1.476 Å for thetransandgaucheconformers, respectively, from the stretching wavenumbers. All of these data are compared with the corresponding quantities obtained fromab initiogradient calculations employing the RHF/3–21G, RHF/3–21G*, RHF/6–31G*, MP2/6–31G*, and/or MP2/6–31 + G* basis sets. Complete equilibrium geometries were calculated for both conformers. The results are compared with corresponding quan

ISSN:0377-0486    

DOI:10.1002/jrs.1250250205

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractRaman and infrared spectra of solid benzyl alcohol and two partially deuterated homologues are reported for the first time. The internal vibrational modes and lattice modes of benzyl alcohol are assigned on the basis of isotopic wavenumber shifts. The spectra of solid benzyl alcohol at low temperatures are shown to be consistent with an ordered non‐centrosymmetric structure, with at least four molecules in the unit cel

ISSN:0377-0486    

DOI:10.1002/jrs.1250250206

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe Raman and infrared wavenumbers of solid HCONH2and DCOND2were measured at 20 K and high temperatures. More peaks were observed in both the lattice and internal mode regions than were expected from the known structure, so the structure was redetermined. The resulting structure is in agreement with earlier determinations, so the extra peaks are attributed to second‐order effects produced by a large anharmonicity associated with the hydrogen bonds. Attempts to model the structural details and the lattice dynamics had only a limited success, which may again be attributed to anharmonic effects and to the basic inadequacies of the model

ISSN:0377-0486    

DOI:10.1002/jrs.1250250207

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe Raman spectra (3100–10 cm−1) of gaseous, liquid and solid acetyl chloride (CH3CClO) and acetyl‐d3chloride (CD3CClO) were recorded and qualitative depolarization values were obtained for the liquid. Additionally, the infrared spectra (3100–50 cm−1) of the gas and solid were recorded. A complete vibrational assignment is proposed for both isotopomers. The assignments are supported by normal coordinate calculations utilizing force constants from theab initiocalculations. The methyl torsion is observed at 162.8 cm−1from which a threefold barrier of internal rotation of 622 cm−1(1779 cal mol−1) is calculated. Utilizing the frequencies for the isolated CH stretching frequencies from the CHD2CClO molecule,r0parameters of 1.093 and 1.096 Å were obtained for the CHsand CHabond distances. The heavy atomr0structural parameters were obtained from previously reported rotational constants from ten isotopomers.Ab initiocalculations were carried out employing the RHF/3–21G*, RHF/6–31G* and MP2/6–31G* basis sets to obtain the vibrational frequencies, force constants, infrared and Raman intensities, structural parameters and barriers to internal rotation. The theoretical results were compared with the experimental

ISSN:0377-0486    

DOI:10.1002/jrs.1250250208

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

ISSN:0377-0486    

DOI:10.1002/jrs.1250250201

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY