bluuebunny/crossref_metadata_2025_split huggingface dataset:
Raman study of the ν(CO) mode of ethyl trifluoroacetate in solution. Reorientational and vibrational relaxation
Authors: Hernanz A. , Troitiño D. 
Published: May 2005

AbstractThe reorientational and vibrational correlation functions of the carbonyl stretching mode of ethyl trifluoroacetate have been determined from its infrared and Raman band shapes in solution in hexane, CCl4, CS2 and CHCl3. Reorientational motion is less hindered in hexane and CCl4 than in CS2 or CHCl3. Kubo and Rothschild's and Oxtoby's stochastic theories have been applied to describe the experimental correlation functions. An intermediate modulation regime is observed in the solvents used. The fastest modulation corresponds to CS2. Fisher and Laubereau's isolated binary collision model for vibrational dephasing does not account for the observed vibrational widths.
Temperature study of intra‐ and inter‐molecular coupling and Fermi resonance constants in the Raman spectra of liquid water using Fourier deconvolution
Authors: Zhelyaskov V. , Georgiev G. , Nickolov Zh. 
Published: May 2005

AbstractThe structure of the Raman OH stretching band of water has been investigated from 4 to 90 °C using a Fourier deconvolution technique. The overlapped components in the isotropic and anisotropic spectra have been resolved. The information on the positions of the components in the deconvoluted spectra was used for calculation of the constants for intra‐ and inter‐molecular coupling and Fermi resonance and for an estimation of the component frequencies according to the model presented. For the first time, the value of the asymmetric Fermi resonance constant and the temperature dependences of all coupling constants have been obtained. Their temperature behaviour is in good agreement with the data in the literature concerning the different phases of water. It was established that the intramolecular coupling constant increases and the intermolecular coupling constant decreases as the temperature increases. The Fermi resonance constant for symmetric components tends to decrease with increasing temperature. The decrease in the symmetric Fermi resonance interaction with increasing temperature is due to the increase in the distance between the unperturbed fundamental and overtone band positions. The asymmetric Fermi resonance constant tends to increase with increasing temperature and this determines the strengthening of the asymmetric Fermi resonance interaction, which exhibits a limiting value at high temperatures.
Use of optical fibres in Raman spectroscopy
Authors: Hendra P. J. , Ellis G. , Cutler D. J. 
Published: May 2005

AbstractA detailed study of the parameters governing the design of an optical fibre system for use in Raman spectroscopy is described. The results have led to the design and construction of a flexible fibre optic remote sampling system which is easily adaptable for use on most commercial instruments. A variety of samples were used to evaluate the performance of the system and have been classified in terms of the efficiency of the new technique relative to more conventional methods of excitation and collection.
Etude par spectroscopie vibrationnelle du compose 4‐nitropyridine N‐oxyde. II—vibrations internes
Authors: Joyeux Marc , Quy Dao Nguyen 
Published: May 2005

AbstractLes spectres d'absorption IR des échantillons polycristallins et les spectres de diffusion Raman en lumière polarisée des monocristaux de 4‐nitropyridine N‐oxyde (NPO) et 4‐nitropyridine‐d4‐N‐oxyde (NPO‐d4) ont été enregistrés entre 200 et 4000 cm−1. Les 36 modes internes de NPO ont été attribués grǎce aux résultats de la théorie des groupes, aux caractères de polarisation observés sur les spectres de diffusion Raman et aux attributions antérieures de molécules analogues. Pour l'attribution des vibrations de NPO‐d4, on a utilisé en plus la règle des produits de Teller‐Redlich. Des couplages dynamiques importants, jusqu'à 13 cm−1, ont été observés pour certains modes. Enfin, les liaisons intermoléculaires dans le cristal sont assez fortes pour rendre inacceptable le modèle du gaz orienté.
Laser Raman and infrared spectra of tartaric acid crystals
Authors: Bhattacharjee R. , Jain Y. S. , Bist H. D. 
Published: May 2005

AbstractA systematic analysis of the IR and Raman spectra of tartaric acid (TA) [HOOC(CHOH)2 COOH], based on standard frequency correlations, deuteration shift and typical characteristics (with respect to intensity and width) of bands due to different modes, is reported. Almost all the vibrational modes of TA appear with two or more split components. The doublet structure of the νCH, νCO and δ modes arises mainly owing to crystallographically distinguishable sites for two identical oscillators. The splitting of other modes [viz. νCO, βCH, ν, ν and τCOOH] originates from differences in the crystallographic fields around the two identical oscillators and resonance interactions between such oscillators. The doublet of δ arises mainly from resonance interactions between two identical oscillators of two identical groups in TA.
Highly resolved depolarization dispersion and excitation profiles of Raman fundamentals of protoporphyrin IX in a cytochrome c matrix
Authors: Bobinger U. , Schweitzer‐Stenner R. , Dreybrodt W. 
Published: May 2005

AbstractNew experimental data for depolarization dispersion (DPD) and excitation profiles (EP) with high spectral resolution (20 cm−1) are provided for Raman fundamentals of protoporphyrin IX in ferrocytochrome c between 17000 and 22 500 cm−1, covering the resonant region of the Q‐bands and the pre‐resonant region of the B‐bands. Both DPD and EPs of the lines at 1312 and 1585 cm−1 (A2g), at 1363 cm−1 (A1g) and at 1621 cm−1 (B1g) exhibit sharp structures. These result from multi‐mode contributions of vibrations which give intensity to the vibronic sideband of the Q‐absorption. On the basis of these highly resolved new data we have shown that the Raman tensor can be formulated in terms of Loudon's strictly time‐dependent perturbation formulation to third order augmented by a fifth‐order term representing the multi‐mode effects. From the EPs, which were measured in absolute units, we obtained values of vibronic coupling parameters for the Raman fundamentals which are consistent with the optical absorption spectra and show that vibronic coupling is weak for this type of molecule.
Theory of inhomogeneous environmental gaussian broadening of resonance Raman excitation profiles for polyatomic molecules in solution
Authors: Zakaraya Merab G. , Maisuradze Gia G. , Ulstrup Jens 
Published: May 2005

AbstractThe effect of static inhomogeneous environmental broadening of Raman excitation profiles and Raman peak intensity distribution of solute molecules was investigated. Homogeneous bradening is represented by Lorentzians and inhomogeneous broadening by Gaussians, where the latter reflect distributions in the purely electronic transition. The Raman scattering cross‐section is calculated analytically, and by means of recent optical bandshape theory for Voigt profiles it can be recast into rapidly converging and easily tractable series expansions well suited for numerical data fitting. The profile expressions also apply to arbitrary values of the broadening parameters and in these respects improve on several previous approaches to inhomogeneous broadening. Notable outcomes are that the excitation profile takes the from of a series of Franck–Condon modulated Voigt profiles when the broadening parameters are small compared with the vibrational frequencies of the Raman‐active modes. In this limit only diagonal terms in the sum over vibrational quantum numbers contribute. When the broadening parameters are not small, non‐diagonal terms are important and lead to additional broadening, profile maximum shifts and bandshape distortion.
Raman spectroscopic study of phase transformation in single crystals of cadmium fluorosilicate hexahydrate
Authors: Thakur Ganesh , Verma A. L. 
Published: May 2005

AbstractA detailed temperature‐dependent Raman study of oriented single crystals of CdSiF6 · 6H2O down to 10 K was made in the region of internal vibrations and lattice modes. The frequency shifts, Iinewidths and intensities of some of the modes associated with the [Cd(OH2)6]2+ and (SiF6)2− ions show abrupt changes at temperatures around 220 K and some doubly degenerate modes split into two components. These studies suggest that the system undergoes a structural phase transition at ca. 220 K.
Raman spectra of some adducts of hexamethylenetetramine
Authors: Santos P. S. 
Published: May 2005

AbstractThe Raman spectra of hexamethlenetetramine (HMTA), HMTA · CBr4, HMTA · CHI3, HMTA · 2CHBr3, HMTA · 2TU and HMTA · 3C6H5OH have been recorded and tentative assignments are given for the observed frequencies. The observed results strongly suggest that there is a correlation between the polarizability of the atom involved in the charge‐transfer interaction in the acceptor molecule and the enhancement of the band assigned to the CNC deformation of the A1 species in the adducts.
Tryptophan Raman bands sensitive to hydrogen bonding and side‐chain conformation
Authors: Miura Takashi , Takeuchi Hideo , Harada Issei 
Published: May 2005

AbstractRaman Spectra of seven tryptophan derivatives in the crystalline state were examined to find Raman bands whose frequencies reflect the strength of hydrogen bonding at the N1H site of the indole ring or the conformation of the indole ring relative to the amino acid backbone. Two indole ring vibrations, W4 around 1490 cm−1 and W6 around 1430 cm−1, showed a correlation between their Raman frequencies and the infrared frequency of the N‐1‐H stretching mode, an indicator of hydrogen bond strength. W4 and W6 increase in frequency with increase in hydrogen bond strength and the frequency variation is particularly large for W6. On the other hand, another indole ring vibration, W3, observed around 1550 cm−1, changes in frequency as a function of the torsional angle, χ2,1, of the C‐2C‐3C‐βC‐α linkage. As the absolute value of χ2,1 becomes larger and the C‐α atom moves away from the C‐2 atom, the W3 frequency increases. In the Raman spectra of proteins excited with visible radiation, the W3 band is usually strong and can be used as a conformational marker, whereas the W4 band is very weak and the W6 band is overlapped by strog scattering due to C–H bending vibrations of aliphatic side‐chains. In UV resonance Raman spectra, however, all these Raman bands are enhanced and may provide key information on the hydrogen bonding and conformation of tryptophan side‐chains.
Raman frequency and intensity studies of liquid H2O, H218O and D2O
Authors: Brooker M. H. , Hancock G. , Rice B. C. , Shapter J. 
Published: May 2005

AbstractRaman frequency and intensity measurements have been performed on liquid water as H2O, D2O and H218O to study the effects of isotope substitution. Intensity data were collected digitally, normalized to account for the temperature and frequency factors and presented in isotropic and anisotropic forms. The frequency and intensity changes are consistent with the predictions of simple reduced mass calculations. In particular, there was no evidence to support the reported breakdown of the Born—Oppenheimer approximation as has been reported for H218O. The isotope invariant sum rule was checked for H216O, H218O and D2O by relative intensity studies for the OH stretching region against an internal sulfate reference peak. Identical values for the isotope invariant sum were obtained for H216O and H218O but the value for D2O was about 30% larger. The difference appears to have its origin in the more highly structured nature of D2O due to smaller anharmonic effects. Accurate frequency shifts among H216O, H218O and D2O are also presented. Surprisingly, the greatest frequency shift which accompanied 18O substitution was in the low‐frequency hydrogen‐bonded region where the band at 192 cm−1 for H2O shifted by 15 cm−1 to 177 cm−1 for H218O. This result confirms previous observations and establishes the origin of this band as a hydrogen‐bonded symmetric stretching mode which involves primarily oxygen displacement. Further support for this assignment comes from the observation that the band at 192 cm−1 is slightly polarized. The effects of intermolecular coupling contribute to the band structure of the internal modes. Frequency differences in the OH stretching region of H2O and H218O suggest that only about 50% of the anisotropic intensity is due to the Raman activity of the ν3 antisymmetric stretching mode while the remainder is due to the symmetric stretching modes of intermolecularly coupled water molecules. A point‐by‐point comparison of the OH stretching region for the isotropic scattered intensity of H2O and H218O revealed that the complete region from 2800 to 3800 cm−1 was shifted equally by 7 cm−1, a fact that suggests that the peak maximum at about 3250 cm−1 is just part of the ν1 symmetric stretching mode and is not primarily due to 2ν2. The effect of intermolecular coupling in the ν2 region of liquid water was confirmed by the difference in the frequency for the isotropic and anisotropic components for each of the isotopic forms of water. For H218O the peak maximum in the isotropic spectrum was at 1619 cm−1 whereas the peak maximum in the anisotropic spectrum was at 1637 cm−1 with the result that in the measured I‖ spectrum the peak maximum was at 1629 cm−1.
Vibrational spectra of some double chromates of the type LnK (CrO4)2
Authors: Baran Enrique J. , Ferrer Evelina G. , Bueno Isabel , Parada Carmen 
Published: May 2005

AbstractRaman and infrared spectra of a series of double chromates of the type Lnk(CrO4)2, with Ln = La, Pr, Nd, Sm, were recorded and discussed with the aid of a factor group analysis. These substances constitute the first example showing the intercalation of v1 between v3 components in crystalline chromates. The spectroscopic results confirm again the structural differences between these chromates and PbCrO4 (synthetic crocoite), which was also investigated for comparison.
Fermi resonance and solvent dependence of the CO moiety of 4‐(dimethylamino) benzaldehyde
Authors: Seehra Jasmeet K. , Jagodzinski Paul W. 
Published: May 2005

AbstractThe Raman spectra of 4‐(dimethylamino)benzaldehyde in the 1550–1750 cm−1 region in seventeen solvents and as a molten liquid were measured. In all cases a multicomponent band was observed in the CO stretching region and these components were analyzed by the solvent variation method for Fermi resonance interactions. Unperturbed vibrational frequencies were calculated, and the frequencies attributed to ν(CO) were plotted against the solvent electron acceptor, number. A dual‐trace plot was observed. These traces were attributed to extrinsic interactions involving both the carbonyl oxygen and the aldehydic hydrogen in solvents of low acceptor number and predominantly the carbonyl oxygen in solvents of high acceptor number. The spectrum of molten 4‐(dimethylamino)benzaldehyde was used to predict an acceptor number of 14 for this molecule. This value was used to differentiate between high and low acceptor numbers for the solvents used in this study.
High‐resolution quasi‐continuous wave inverse Raman spectrometer. Spectrum of CH3D in the CD stretching region
Authors: Bermejo D. , Santos J. , Cancio P. , Doménech J. L. , Domingo C. , Orza J. M. , Ortigoso J. , Escribano R. 
Published: May 2005

AbstractThe construction of a spectrometer for high‐resolution stimulated Raman spectroscopy is reported and the accuracy of wavenumber determination achievable is discussed. A Doppler‐limited spectrum of the CD stretching band (Q‐branch) of the CH3D molecule in the 2200 cm−1 region was recorded. Most of the observed transitions have been assigned and some rotational‐vibrational constants have been refined.
Pressure dependence of Raman spectra from the garnet end‐members pyrope, grossularite and almandite
Authors: Mernagh Terrence P. , Liu Lin‐Gun 
Published: May 2005

AbstractThe synthetic end‐member garnets pyrope, grossularite and almandite were studied at high pressures using Raman spectroscopy. Previous vibrational mode assignments for these garnets were modified to account for the splitting of some degenerate modes at high pressures and other observed pressure effects. The band widths indicate that residual stresses are present in the garnets at ambient conditions and that these diminish as they approach their formation pressures.No pressure‐induced phase changes were observed and mode‐gruneisen parameters calculated from the pressure shifts and the bulk modulus indicated that these garnets all behave similarly with increasing pressure. The Raman bands varied linearly with increasing pressure and a slope of 0.40 ± 0.01 cm−1 kbar−1 was obtained for the most intense A1g mode of each garnet. These observations allow us to predict that natural aluminosilicate garnets, included in diamonds or other transparent minerals, may be used to monitor in situ pressures up to 150 kbar, provided that a Raman spectrum can be obtained from a similar garnet at ambient conditions.
Single‐crystal Raman studies on Sr(ClO3)2 and BrO3− and IO3− ions matrix isolated in Sr(ClO3)2
Authors: Lutz H. D. , Alici E. , Kellersohn Th. 
Published: May 2005

AbstractSingle‐crystal Raman spectra of Sr(ClO3)2 and Sr(ClO3)2 crystals with matrix isolated BrO3− and IO3− guest ions are presented and discussed in terms of TO/LO splitting and distortion of the XO3− ions. Because of the large distortion of these ions in the structure (site symmetry C1), no intra‐ionic vibrational coupling of the XO vibrations to symmetric (ν1) and asymmetric (ν3) stretching modes occurs. This is proved by oriented gas model calculations of the intensities of the guest ion Raman bands. The infrared and Raman spectra of polycrystalline samples of the isostructural compounds Ba(ClO3)2, Ba(BrO3)2 II, Pb(ClO3)2 and Pb(BrO3)2 are also reported.
Spectra and structure of small ring compounds. Part LVII—Raman and infrared spectra, vibrational assignment and ab initio calculations of cyclopropyltrifluorosilane
Authors: Little T. S. , Qtaitat M. , Durig J. R. , Dakkouri M. , Dakkouri A. 
Published: May 2005

AbstractThe Raman (3500–20 cm−1) and infrared (3500–40 cm−1) spectra of gaseous and solid cyclopropyltrifluorosilane have been recorded. Additionally, the Raman spectrum of the liquid has been recorded and qualitative depolarization ratios have been obtained. From these data a complete assignment of the normal vibrational modes is provided. The fundamental vibrational frequencies have also been calculated from ab initio Hartree‐Fock calculations with the 3–21G* basis set. The force field obtained from these calculations has been used to carry out a normal coordinate analysis with a chosen set of symmetry coordinates. The molecular structure and potential surface governing internal rotation of the SiF3 moiety have been calculated using both the 3–21G* and 6–31G* basis sets. Additionally, the SiF3 torsional mode has been observed in the far‐infrared spectrum of the gas as a broad band centered at 46 cm−1 and from this frequency a periodic threefold barrier to internal rotation has been determined to be 420 cm−1 (1.2 kcal mol−1). These results are compared with corresponding quantities for some similar molecules.
Raman spectra and ab initio calculations for methyl nitrite and methyl‐d3 nitrite
Authors: Stidham Howard D. , Guirgis G. A. , van der Veken B. J. , Sheehan T. G. , Durig J. R. 
Published: May 2005

AbstractThe Raman (4000–10 cm−1) and infrared (4000–80 cm−1) spectra of methyl nitrite, CH3ONO, and methyl nitrite‐d3 were recorded in the gas and solid phases. Additionally, the Raman spectra of the pure liquids were recorded and qualitative depolarization values were obtained. Support for the interpretation of these new data is provided by ab initio calculations using the 6–31G* basis set. Complete equilibrium geometries have been determined for both conformers, as well as structures for every 30° rotation about the NO bond. These calculations give a cis/trans barrier of 4015 cm−1 (11.5 kcal mol−1), a trans/cis barrier of 3504 cm−1 (10.0 kcal mol−1) and an enthalpy difference between conformers of 511 cm−1 (1.5 kcal mol−1) with the cis form being more stable. From a variable temperature Raman study of liquid methyl nitrite‐d3 it is concluded that the cis form is also more stable in this phase with an enthalpy difference between conformers of 262 ± 3 cm−1 (750 ± 9 cal mol−1). A complete assignment of the vibrational fundamentals is proposed based on band contours, depolarization values, group frequencies and shift factors for the two isotopomers. These assignments are supported by normal coordinate analyses using the ab initio force fields to obtain frequencies and potential energy distributions for both conformers.
High‐pressure Raman study of liquid and solid ethanol at pressures up to 17 GPa
Authors: Shimizu H. , Nakamichi Y. , Sasaki S. 
Published: May 2005

AbstractHigh‐pressure Raman spectra of liquid and solid ethanol were measured at pressures up to 17 GPa and 300 K in a gasketed diamond anvil cell. The frequencies of in‐phase and out‐of‐phase OH stretching vibrations which characterize the hydrogen bond along the zig‐zag chain decrease with increasing pressure with slopes(dν/dP) of −14.3 and −12.4 cm−1 GPa−1, and they overlap with the CH stretching mode at about 11 and 17 GPa, respectively. No solid‐solid phase transition was observed at pressures up to 17 GPa.
Vibrational study of phase transitions in (C3H7NH3)2PbCl4
Authors: Abid Younes , Kamoun M. , Daoud A. , Romain F. 
Published: May 2005

AbstractInfrared and Raman spectra (5–3500 cm−1) of polycrystalline samples of (C3H7NH3)2PbCl4 and of its deuterated derivative were investigated in the temperature range 90–300 K. An assignment of the observed bands at room temperature is proposed. A temperature dependence study of the frequencies, ν, and half‐widths, Δν1/2, of some low‐frequency Raman bands revealed two phase transitions at about 110 and 170 K, whereas the deuterated compound showed only one phase transition at about 150 K in the same temperature range. These transitions are believed to be governed by libration of the cation coupled with NH3 group jumps between different potential wells. The value of activation energy, E0 = 3.2 kJ mol−1, was calculated from the plot of Δν1/2 νs. temperature; it is of the same order of magnitude as the potential barrier, V6 = 3.53 kJ mol−1, calculated from the torsional frequency of NH3+ (288 cm−1).
Adsorption and reaction of 4‐methoxycinnamonitrile on a silver surface: A surface‐enhanced Raman spectroscopic study
Authors: Chun Hyun Aee , Yi Sung Soo , Kim Myung Soo , Kim Kwan 
Published: May 2005

AbstractSurface‐enhanced Raman scattering of cis‐ and trans‐4‐methoxycinnamonitrile (4MCN) was investigated in aqueous silver sols. Both isomers adsorbed on the silver surface via the cyano group. The adsorption strength for the cis isomer appeared to be greater than that for the trans isomer. However, cis‐4MCN, adsorbed selectively on the silver surface, was readily converted to the trans isomer via a laser‐assisted surface reaction. The exact mechanism of the photoisomerization is not yet completely understood. It is thought that the reaction occurs via the absorption of a single visible photon which is in resonance with the low‐energy tail of the broadened absorption band of the adsorbed cis isomer.
Application of Raman spectroscopy to industrial membranes. Part 1—polyacrylic membranes
Authors: El Boukari M. , Bribes J.‐L. , Maillols J. 
Published: May 2005

AbstractIndustrial membranes (made of polyacrylic acid chains grafted onto a polyethylene matrix), immersed in heavy water, were studied by Raman spectroscopy. The homogeneity of the graft density was sufficient to permit the determination of relative graft rations of different samples. Plots of measured ionization versus the pH of solutions in equilibrium with immersed membranes lad to intrinsic pK determinations. For this kind of membrane, it was established that the average lengths of the polyacrylic chains are of the same order of magnitude. Consequently, the different graft ratios depend only on graft density.