摘要:

AbstractThe temperature dependence of the Raman line width of the ν1and ν2modes of the SO 42−ion in ammonium sulphate was investigated. A sudden change in the full width at half maximum intensity (FWHM) of both bands is observed at the ferroelectric transition point of the crystal. The results are explained in terms of the coupling between phonons originating from these modes and NH4+ion pseudo‐spins. The results obtained from pseudospin–phonon coupling formulations agree satisfactorily with the experimental results. The coupling also accounts for the temperature dependence of spontaneous pol

ISSN:0377-0486    

DOI:10.1002/jrs.1250210602

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractSurface‐enhanced Raman (SER) spectra of nucleotides, calf thymus DNA and plasmid pAO 3 in the supercoiled and relaxed conformations adsorbed on colloidal silver were analysed. Two different techniques were used for the preparation of the silver hydrosol. All the compounds were adsorbed on the standard hydrosol with very low specificity with respect to the chemical nature of the adsorbate. ‘Activation’ of the standard hydrosol by Cl−ions induced adsorption sites highly specific to the adenine nucleotides. It was demonstrated that recording of highresolution SER spectra of nucleic acids and their components at 10−13g is possible and that ‘activation’ of the silver hydrosol permits the selective detection of the sites of destabilization of double‐stranded helices and identification of the nucleotides

ISSN:0377-0486    

DOI:10.1002/jrs.1250210603

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe electronic (900–250 nm), infrared and Raman (600–10 cm−1) spectra of polycrystalline samples of NbS3were investigated. A complete vibrational assignment is proposed and the band wavenumbers are compared for NbS3and the related ZrS3and NbS2Cl2. All the assignments have been checked by a complete valence force field calculation including intrachain, interchain and interlayer contributions. The potential energy distributions and mean square vibrational amplitudes so calculated and the values of force constants are in agreement with the two‐dimensional character of the lattice dynamics in NbS3.In addition, an extensive resonance Raman study has been performed using various exciting radiations in the visible (676.4–457.9 nm) and near‐UV regions (363.8 and 351.1 nm). The experimental unresolved Raman excitation profiles in the contour of two low‐energy electronic transitions (λmax≈︁ 600 and 560 nm) exhibit interesting interference and exact resonance effects depending on the nature of the vibration. Taking account of multi‐state interference phenomena and inhomogeneous broadening effects, these profiles compare well with the computed ones on the assumption of weakly displaced oscillators. This allows conclusions to be drawn about the scattering mechanisms and the nature of the first elect

ISSN:0377-0486    

DOI:10.1002/jrs.1250210604

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractAn effective dielectric constant for metal island films has been evaluated using a parametrization of the optical property in terms of the packing factor, the film thickness and a distribution of axial ratios for spheroidal particles. Electron micrographs and plasmon absorption spectra of discontinuous films served as references for parametrical fitting. Enhanced Raman intensities of molecules oriented on the surface of oblate spheroids and a backscattering geometry are discussed.

ISSN:0377-0486    

DOI:10.1002/jrs.1250210605

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe IR, micro‐Raman and Fourier transform (FT) Raman spectra of 3‐O‐(3‐hydroxypropyl)‐17β‐estradiol and the two (α and β) diastereomers, produced by coordination of a Cr(CO)3moiety to the arene A ring of the steroid, are presented. The three compounds exhibit spectra typical of arene hormonal steroids and the α‐ and β‐diastereomers can be readily distinguished from one another, especially by their FT‐Raman spectra in the CO stretching region which, unlike the corresponding micro‐Raman data, are not significantly masked by the presence of strong fluorescence backgrounds. This distinction is important since the α‐diastereomer is a useful IR estrogen‐receptor marker, wher

ISSN:0377-0486    

DOI:10.1002/jrs.1250210606

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe Raman (3100–10 cm−1) and infrared spectra (3100–30 cm−1) of propionyl fluoride in the gas and solid phases were recorded. Additionally, the Raman spectrum of the liquid and the qualitative depolarization ratios were also obtained. From these data a complete vibrational assignment is proposed for ans‐trans/gaucheequilibrium in the gas and liquid phases, with thes‐transconformer (the CH3moiety iss‐transto the fluorine atom) being the most stable form in both of these physical states and the only form present in the solid phase. A new potential function has been calculated from the data previously obtained from the far‐infrared spectrum of the gas. The determined potential coefficients areV1= 328 ± 6,V2= 239 ± 8,V3= 417 ± 3,V4= 30 ± 3 andV6= −4 ± 2 cm−1, and values of 720 ± 8 (2.06 ± 0.02 kcal mol−1) and 297 ± 9 cm−1(0.85 ± 0.02 kcal mol−1), respectively, were obtained for thes‐transtogaucheandgauchetogauchebarriers to internal rotation of the CFO moiety. Additionally, thes‐transconformer was determined to be 448 ± 17 cm−1(1.28 ± 0.05 kcal mol−1) more stable than thegaucheconformer. From the study of the Raman spectrum obtaind for the liquid at different temperatures, a value of 267 ± 12 cm−1(0.76 ± 0.03 kcal mol−1) was determined for ΔHbetween the two conformers. The structural parameters, conformational stabilities, barriers to internal rotation and fundamental vibrational frequencies which were determined experimentally are compared with those obtained fromab initioHartree‐Fock gradient calculations employing both the RHF/3‐21G and RHF/6–31G* basis sets, and with the cor

ISSN:0377-0486    

DOI:10.1002/jrs.1250210607

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractBrillouin scattering at room temperature has been used to determine the elastic constant tensor for the trissarcosine calcium chloride (TSCC): the frequency used was near 18 GHz. The sound velocity polar diagrams show an interesting behaviour: the quasi‐longitudinal and the quasi‐transversal branches are degenerate for a propagation direction inside the (010) pl

ISSN:0377-0486    

DOI:10.1002/jrs.1250210608

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe first measurements of vibrational Raman optical activity (ROA) have been performed employing a forward scattering geometry. Forward‐scattered ROA spectra of (+)‐trans‐pinane and (−)‐β‐pinene are presented as first examples. Comparison with the corresponding backward‐and right‐angle‐scattered spectra confirmed that the bond polarizability theory of ROA is a good approximation fortrans‐pinane, and has identified unequivocally a large isotropic contribution to the ROA in β‐pinene bands at 716 and 765 cm−1ascribed to interactions between the olefinic methylene twist and a skeletal mode of the pinane structure. Unless large isotropic contributions are present, which is unusual, forward scattering is by far the least favourable of the ROA measurement strategies, which might explain the failure of recent attempts to observe ROA in coherent ant

ISSN:0377-0486    

DOI:10.1002/jrs.1250210609

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractMicro‐Raman spectra of crystalline uridine were obtained at room temperature and at pressures approaching 40 kbar with the aid of a diamond‐anvil cell. There is evidence for a phase transition at about 12 kbar which is probably associated with changes in the hydrogen‐bonding interactions between the two molecules present in the unit

ISSN:0377-0486    

DOI:10.1002/jrs.1250210610

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

ISSN:0377-0486    

DOI:10.1002/jrs.1250210611

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY