摘要:

AbstractThe Raman spectra of thev1(SO 42−) band in aqueous solutions of Li2SO4, Na2SO4and K2SO4as a function of concentration at room temperature and for fixed concentrations in the temperature range 5—85°C were studied. It was found that the molar scattering coefficient for SO 42−is virtually independent of the concentration and temperature in the studied range. Nevertheless, thev1(SO 42) band shows some asymmetry on the high‐wavenumber side for Li and Na and on the low‐wavenumber side for K, which for these last two cases has not previously been reported. Moreover, the band position seems to be correlated with the sign and amount of the asymmetry as the concentration increases. On the other hand, temperature does not have a great effect on the band profile. In the case of Na and K, there is little narrowing of the band, whereas for Li there is slight broadening and an increase in the asymmetry. Quantitative analysis of these changes was performed using the vibrational correlation function. This was modelled considering the distribution of sulphate oscillators in the aqueous media as a convolution product of an unperturbed distribution by a perturbation function. This last function assumes a feedback mechanism in which the main parameters are the coupling energy and the fraction of the distribution having interactions. The dependence of these parameters and of the Gaussian and Lorentzian contributions to the band profile with concentration and temperatu

ISSN:0377-0486    

DOI:10.1002/jrs.1250260812

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractRecently, anomalies concerning both intensities and peak positions of Raman bands in the carbonyl stretching region of liquid mixtures of different isotopomers of formamide were reported. More detailed investigations have now been performed for liquid mixtures of HCONH2and H13CONH2, and Raman spectra of mixtures of DCONH2and DCOND2in the carbonyl stretching region are presented. In the system DCONH2‐DCOND2, collapse of the isotropic carbonyl bands was observed in the mixtures as previously reported for HCONH2‐HCOND2and HCOND2‐DCOND2. The system HCONH2—H13CONH2shows anomalous intensities compared with those expected for simple binary mixtures. However, this system does not show collapsing carbonyl bands in the isotopomeric mixtures. The phenomenon of collapsing bands can be explained in terms of a model known as mutual entr

ISSN:0377-0486    

DOI:10.1002/jrs.1250260813

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe UV—visible (340—800 nm) and Raman spectra (10—900 cm−1) obtained using various laser exciting radiation of a powder sample of the misfit compound (PbS)1.12VS2were investigated. In agreement with x‐ray data, vibrational assignments are proposed for most of the internal and external modes of the ‘PBS’ and ‘VS2’ layered sublattices and they were extensively compared with those in the related titanium‐containing compound in order to appreciate the interactions due to the ‘PbS’ donor part of the structure. Owing to the incommensurate structure of (PbS)1.12VS2, new slightly resonance exhanced Raman signals are detected and they can be explained by thek= O, ±q* selection rules (q* is the modulation vector) as in a previous study of (SnS)1.17NbS2and (PbS)1.18TiS2compounds. These observations are again confirmed by lattice dynamics calculations which reproduce the essential features of the experimental data and allow one to estimate the strength of

ISSN:0377-0486    

DOI:10.1002/jrs.1250260814

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractMicro resonance Raman spectra of a series of synthetic carotenoids and of a large number of bird's feathers which contain various kinds of carotenoids were analysed on the basis of the effective conjugation coordinate (ECC) theory. The data obtained on parrots provide the first structural data on the chemical nature of the pigments embedded in their feathers, and show that these pigments are unmethylated polyene molecules. Data on the molecular orientation of the carotenoids and on the presence of different pigments in the same feather are presented and discussed.

ISSN:0377-0486    

DOI:10.1002/jrs.1250260815

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractSurface‐enhanced resonant Raman scattering and Fourier transform surface‐enhanced Raman scattering of Langmuir‐Blodgett monolayers of the green and blue forms of octa‐(15‐crown‐5)‐lutetium bisphtalocyanine prepared on gold island films are reported. The spectroscopic characterization was completed by measuring the Raman and Fourier transform infrared spectra of dispersions of the materials in KBr matrices. An empirical vibrational assignment of the observed fundamen

ISSN:0377-0486    

DOI:10.1002/jrs.1250260816

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractA continuous‐wave CARS spectrometer was equipped with a new frequency‐stabilized argon ion ring laser and better stabilization for the tunable dye laser was introduced. Special quartz sample cells with Brewster angle windows were placed in the focal region of the argon ion ring laser. A new data acquisition system was installed which allows the simultaneous recording of CARS signals and calibration spectra and the subsequent evaluation of the data. An instrumental resolution of less than 0.001 cm−1and a wavenumber accuracy of about ± 0.006 cm−1were achieved. As an example of the performance of the spectrometer, the CARS spectrum of ethane was measured in the region of the CH vibrations at pressures between 95 and 1.9 kPa. The spectra were compared with the stimulated Raman spectrum published

ISSN:0377-0486    

DOI:10.1002/jrs.1250260817

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractAs shown in a previous paper, Neumann's principle allows one to calculate the forms of property tensors and tensorial covariants of classical point groups. A simple extension of this principle permits one to determine also the corresponding expressions for magnetic point groups. In this paper the results for the crystallographic point groups are given.

ISSN:0377-0486    

DOI:10.1002/jrs.1250260818

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractLithium perchlorate solutions in acrylonitrile (propenenitrile), in a range of concentration between 1 and 6 molal, were studied by using Fourier transform Raman spectroscopy. The new band in thev(CN) region proceeding from the bound species Li+… (acrylonitrile)nand the modifications in the C—C stretching band were studied in detail by means of deconvolution and band‐fitting procedures. An average solvation number ofca. 2.3 was obtained without any correction for the ion pairing. The data obtained in the analysis of the perchlorate anionv1(symmetric stretch) band allow us to quantify the concentration of the different species (free perchlorate, solvent‐separated ion pairs and contact ion pairs) present, and to obtain a more realistic solvation number for the lithium ion in acrylonitrile solutions. This solvation number was estimated at 3.

ISSN:0377-0486    

DOI:10.1002/jrs.1250260819

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractA simple method for the determination of enantiomeric excess is described. It is based on depolarized Raman optical activity (ROA) measurements in right‐angle scattering employing the incident ciruclar polarization (ICP) modulation approach. The accuracy of this method was assessed utilizing α‐pinene as a chiral test compound. The four α‐pinene ICP ROA signals associated with the Raman bands observed atca. 772, 787, 887 and 929 cm−1were selected to establish a linear relationship between ROA signal strength and enantiomeric composition for a set of calibration mixtures containing both α‐pinene enantiomers. Using this relationship, a (+)‐α‐pinene sample content of 16.3% was determined for a blind mixture containing 83.6% (1S)‐( — )‐α‐pinene and 16.4% (1R)‐(+)‐α‐pinene. Similary, utilizing additional spectral subtraction procedures, a (+)‐α‐pinene sample content of 1.5% was estimated for a test mixture consisting of 50.1% (1S)‐( — )

ISSN:0377-0486    

DOI:10.1002/jrs.1250260820

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe backscattering in‐phase dual circular polarization (DCPI) Raman and Raman optical activity (ROA) for a series of terpene molecules is reported. The selected molecules were studied in three groups of closely related structures and correlations between ROA features and structural elements among molecules within these groups are discussed. One aim of this study was to uncover additional details regarding the sensitivity of ROA to stereostructural features in molecules and to elucidate further the degree of local character of this new stereochemical probe. Another was to compare the backscattering DCPIROA intensities reported here with those obtained using depolarized right‐angle incident circularly polarized (ICP) ROA for some of the same molecules more than a decade

ISSN:0377-0486    

DOI:10.1002/jrs.1250260821

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY