摘要:

AbstractThe infrared and laser Raman spectra of β‐LiVOPO4and NaVOPO4were recorded and are briefly discussed with the aid of factor group analyses, based on recently reported structural data. Some spectroscopic features related to the characteristics of the VO and PO bonds in these compounds are also commente

ISSN:0377-0486    

DOI:10.1002/jrs.1250250302

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractOxygenated CdTe films prepared by r.f. sputtering have been shown to have band gap energies between 1.48 and 3.35 eV, depending on the amount of oxygen incorporated in the CdTe matrix. Samples with oxygen concentrations above 7 at.% are amorphous, whereas those with oxygen concentrations below 7 at.% are polycrystalline, as determined by x‐ray and Raman measurements. The Raman spectra of the polycrystalline samples show that there isca.4 at.% Te in the form of inclusions under high pressure, which is relatively easy to detect owing to the enhanced Raman cross‐section of Te. The Raman spectra of the amorphous samples is dominated by a single broad band at 159 cm−1. The fact that tellurates in general show a similar band, in spite of their different vibrational density of states, indicates that it corresponds to TeTe bonds in the amorphous

ISSN:0377-0486    

DOI:10.1002/jrs.1250250303

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractBecause of the importance of developing an active substrate for surface‐enhanced Raman (SER) spectroscopic applications, a silver‐coated filter‐paper substrate was prepared for surface‐enhanced Raman scattering (SRS) by using a chemical reduction method at room temperature. Optimization of the silver deposition time was achieved by usingp‐nitrophenol (PNP) as an analyte. Its performance as an SERS‐active substrate was tested using PNP,p‐chlorobenzoic acid,m‐chlorobenzoic acid ando‐chlorobenzoic acid. To overcome the problem of low enhancement when a dipping method was adopted for sample applications, a silver‐coated alumina‐based substrate was prepared. The new substrate was found to exhibit strong SERS with both the solution and the dipping methods for sample applications of PNP. Using the new substrate, the limit of detection for methyl red was esti

ISSN:0377-0486    

DOI:10.1002/jrs.1250250304

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractA micro‐Raman probe was used to characterize thin films of barium titanate synthesized by metallo‐organic decomposition and rapid thermal annealing techniques. All films were found to be polycrystalline aggregates with perovskite as the primary phase. The optimum film processing procedure as evidenced by the micro‐Raman probe was a combination of rapid thermal annealing at 950°C in an oxygen or argon atmosphere. Fourier transform infrared spectra indicated that samples annealed in a vacuum show higher carbon contamination than those receiving the same heat treatment in an oxygen or argon atmo

ISSN:0377-0486    

DOI:10.1002/jrs.1250250305

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe Raman (3100–10 cm−1) and infrared (3100–30 cm−1) spectra of fluorocarbonyl isocyanate, FC(O)NCO, were recorded for the gas and solid. Additionally, the Raman spectrum of the liquid was recorded and qualitative depolarization values were obtained. The observed bands are assigned on the basis of the more stablecisconformer (isocyanate groupcisto the carbonyl bond) in the fluid states but only thetransconformer remains in the annealed solid. From temperature dependence studies of the Raman spectra of the gas and liquid, two pairs of conformer peaks were used to determine ΔHvalues of 258 ± 47 cm−1(738 ± 134 cal mol−l) and 140 ± 29 cm−1(400 ± 83 cat mol−1), respectively, with thecisconformer the more stable rotamer in both phases. Additionally, variable‐temperature studies of the infrared spectrum of the sample dissolved in liquified Kr gave ΔH= 150 ± 28 cm−1(429 ± 80 cal mol−1), which should closely represent the ΔHvalue for the gas. A complete vibrational assignment is proposed for both conformers based on infrared bard contours, Raman depolarization data, group frequencies, relative intensities and normal coordinate calculations. The experimental conformational stability, barriers to internal rotation, structural parameters and fundamental vibrational wavenumbers were compared with those obtained fromab initiogradient calculations employing the RHF/3–21G, RHF/6‐31G* and /or MP2/6‐31G* basis sets and to the corresponding quantities

ISSN:0377-0486    

DOI:10.1002/jrs.1250250306

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractFourier transform (FT) IR and FT‐Raman spectra for purine and its N‐, C8‐ and N‐ and C8‐deuterated analogues and for that15N‐substituted on the pyrimidine ring are reported. Experimental data are interpreted by reference toab initio‐calculated wavenumbers for normal modes of both N7H‐ and N9H‐purines. The latter were obtained from normal coordinate analyses carried out on the basis ofab initio3–21G force fields using the optimized geometry. The effect of hydrogen bonding on the discrepancy between calculated and observed wavenumbers for normal modes was analysed. Considering the solid N7H‐purine, the observed15N shifts for FT‐IR bands often agree with those calculated for the corresponding normal modes. Several weak bands are tentatively assigned to the N9H tautomer, presumably present in small amounts in solution and also in the solid in the cas

ISSN:0377-0486    

DOI:10.1002/jrs.1250250307

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractPolarized Raman spectra of BaCl2· 2H2O and their assignments are reported. The Raman intensity was analysed by means of the pair approximation and the many‐body interaction among induced dipoles. It was found that the many‐body treatment is more quantitative than the pair approximation, although the agreement between the observed and calculated polarized spectra is still incomplete. The difference between the two methods is discu

ISSN:0377-0486    

DOI:10.1002/jrs.1250250308

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

ISSN:0377-0486    

DOI:10.1002/jrs.1250250301

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY