摘要:

AbstractThe low‐wavenumber Raman spectrum of pyrazinic acid (PA) crystal (orthorhombic,Pna21/D 2h16) was measured in the range 200–10 cm−1. Twelve Raman‐active lattice modes of crystalline PA were observed. Their tentative assignments in terms of hydrogen bond motion are reported. The intra‐ and inter‐chain translational modes were assigned using the isolated single‐chain (Cs) approximation, whereas the rotational modes were separated out mainly on the basis of their polarization behaviour, intensities and the shapes of thei

ISSN:0377-0486    

DOI:10.1002/jrs.1250251002

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe Raman depolarization ratios of carbon monoxide were measured via the zeroth spectral moment,Mo(integrated intensities), and simple peak‐height determinations under isothermal conditions (323 K) over a pressure range of 20–2400 bar in a mixture of CH4and CO. These conditions correspond to densities ranging from 0.75 to 24 mol I−1. The measurements were carried out so that the depolarization ratios being measured in other experiments from the ν1totally symmetric stretching mode of supracritical methane could be corrected for instrumental depolarization effects. The values near a pressure of 1 bar have been calculated and measured for CO by several sets of workers. The cell windows were float glass and as a result they are known to contribute much less than quartz to depolarization. Float glass windows cause only a 0.5% error in scrambling uncertainty of the polarized light exiting the high‐press

ISSN:0377-0486    

DOI:10.1002/jrs.1250251003

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractA colloidal silver oxide hydrosol was prepared for surface‐enhanced Raman scattering (SERS). Its performance as a SERS‐active substrate was tested using benzoic acid and 1,1′‐diethyl‐2,2′cyanine iodide as analytes. SERS and surface enhanced resonance Raman scattering were observed for the adsorbed samples. In the preparation of the sol, the relative amounts of reagents should be an important factor in affecting the surface enhancement of the substrate. The surface enhancement activity of the colloidal hydrosol might indicate that silver oxide films generated in the electrochemical oxidation of a silver electrode could enhance the Raman spectra of adsorbed molecules and/or passi

ISSN:0377-0486    

DOI:10.1002/jrs.1250251004

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractInvestigations of the Raman spectra of lead–lanthanum–zirconate‐titanates (PLZT)x:95:5 (x= 0.5, 1, 2, 3 and 4 wt.% La2O3) ceramics over a range of temperature from 10 K to room temperature are presented. With increasing temperature the intensity of the Raman spectra, corrected for the Bose population factor, is lower above the transition temperatureT0= 130 K; this intensity lowering is characteristic of disorder‐induced spectra. This temperature dependence is interpreted by means of the theory of fluctuating clusters in the low‐temperature phase and the order parameter belowT0was determined. Associated with this phase transition, it was found that some softening effects are present in the vibrational wa

ISSN:0377-0486    

DOI:10.1002/jrs.1250251005

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractVibrational spectra of zinc tris(thiourea) sulphate (ZTS), a new semiorganic non‐linear optical crystal, were recorded to determine the symmetries of molecular vibrations. The observed Raman and infrared bands are assigned to molecular vibrations of thiourea, sulphate groups and Zn(thiourea)3SO4tetrahedra. The Raman spectra are interpreted in the light of crystal structure data. Modifications in the IR spectra of thiourea due to metal complexations are discusse

ISSN:0377-0486    

DOI:10.1002/jrs.1250251006

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractSelf‐absorption occurs in near‐infrared Fourier transform (NIR‐FT) Raman spectroscopy when the absolute frequency of a Raman band coincides with an NIR absorption band of the scattering material. This is manifested by selective attention of specific Raman bands, the degree of which depends on the sample pathlength, concentration and position in the laser beam. These factors can introduce serious errors in quantitative FT Raman applications unless care is taken. This paper describes a simple analysis which allows quantitative predictions of the effects of varying sample concentration and collection optics geometry. The predictions for concentration variation have been validated by experiment. A consideration of the experimental design required to minimize self‐absorption indicates that this will also reduce instrument sensitivity and ease of alignment; therefore, there is a trade‐off between optimizing instruments for quantitative applications whilst maintaining sensitivity and ea

ISSN:0377-0486    

DOI:10.1002/jrs.1250251007

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractReliable assignments for normal modes of adenine, 9‐methyladenine, guanine and 9‐methylguanine were obtained fromab initio3–21G force fields and optimized geometries. In addition, relative itensities were calculated at resonance with the excited states corresponding to the lowest energy π–π * orbital excitations from the change in bond order and theL−1matrix. Wavenumbers and relative intensities for resonance Raman active modes Were compared with those previously observed for resonance Raman enhanced bands of AMP and GMP in aqueous solutions obtained with excitation near the absorption band at 260 nm and below. There is satisfactory agreement between observed and calculated relative intensities for the guanine residue. In particular, the large increase in intensity observed for the CO stretching band at 1670 cm−1with excitation below 220 nm is correctly reproduced. On the other hand, there is less agreement for the adenine residue where the distribution of intensity at resonance according to theAterm of the resonance Raman theory is probably altered by the presence of vibr

ISSN:0377-0486    

DOI:10.1002/jrs.1250251008

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractChanges in the isotropic and anisotropic component profiles of the O—D stretching bands of D2O were studied in the range 0–0.5 mole fraction (m.f.) of 1,4—dioxane. The contribution of the CH Raman band of dioxane was subtracted using Raman spectra of dioxane—water mixtures in the same concentration range. A Fourier deconvolution technique was employed to resolve the overlapped components in the spectra. The information on the positions of the components in the isotropic spectra was used to fit them with symmetric components of mixed Gaussian—Lorentzian type. The wavenumbers of the resolved components in the isotropic and anisotropic spectra and the ratio of the intensities of the symmetric Fermi resonance components in the isotropic spectra were used to determine the concentration dependence of intermolecular, intramolecular and Fermi resonance parameters. The intermolecular and intramolecular interaction constants do not change significantly up to about 0.07–0.10 m.f. of dioxane and then gradually decrease. The Fermi resonance constantWdoes not change noticeably over the concentration range studied. The wavenumbers of the unperturbed O–D oscillator exhibits two different rates of increase with concentration of dioxane. The observed variations in the analysed parameters are interpreted in terms of hydrophobic hydration, hydrophobic interaction and hydrogen bonding in dioxane

ISSN:0377-0486    

DOI:10.1002/jrs.1250251009

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe Raman spectra of solutions of TeCI4in HCI up to 12 mol I−1show a changing pattern of bands consistent with a mixture of complexes, including [TeCI6]2−and [TeCI4(OH)]−. High‐field125Te NMR spectra at 126.24 MHz of these aqueous solutions consist of a single bind, showing that the TeIVspecies are in rapid equilibrium, which moves upfield within the range + 1550 to + 1400 ppm as the HCI concentration is increased. Solvent extraction with diethyl ether selects a single species from TeIVHCI solutions. This is identified as the complex acid HTeCI4(OH) by a Raman spectrum marked by νs(TeCI) = 289 cm−1and ν(TeO) = 667 cm−1, and a characteristic125Te resonance, δ =

ISSN:0377-0486    

DOI:10.1002/jrs.1250251010

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

ISSN:0377-0486    

DOI:10.1002/jrs.1250251001

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY