bluuebunny/crossref_metadata_2025 huggingface dataset:
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

The 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

A 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

Les 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

A 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

New 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

The 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

A 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

The 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

Raman 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

Raman 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

Raman 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

The 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

The 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

The 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

Single‐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

The 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

The 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

High‐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

Infrared 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

Surface‐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

Industrial 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.
Temperature and pressure dependence of the ν1 band of water vapour by high‐resolution inverse Raman spectroscopy
Authors: Greenhalgh D. A. , Rahn L. A.
Published: May 2005

The Raman spectrum of the ν1 band of water vapour at pressures up to 300 τ and for five temperatures between 300 and 1200 K was measured using high‐resolution inverse Raman spectroscopy. Self‐broadening coefficients were determined for 59 distinct lines from J = 0 to J = 11. The temperature dependence of these coefficients was also determined for most of these lines and was compared with previously published calculations. Spectral regions where deviations have been previously observed between measured and calculated CARS spectra of the ν1 band were studied in detail. Corrections to line positions and relative intensities are suggested for improving the current water vapour spectral model.
Raman and IR spectra of Te(OH)6·2Na3P3O9·6H2O
Authors: Philip Daizy , Aruldhas G. , Mathew Xavier , Nayar V. U. , Boudjada N. , Lambert‐Andron B.
Published: May 2005

Raman and IR spectra of Te(OH)6·2Na3P3O9·6H2O were recorded and analysed. The vibrational bands due to P3O, TeO6 octahedra and water molecules were identified. It was found that P3O has a ring structure in the compound. The TeO6 group and P3O were found to coexist independently in the crystal. Further, the water molecules are non‐equivalent in the unit cell.
Raman spectroscopic study of hexacarbonyl molybdenum(0) entrapped in zeolite cages
Authors: Brémard C. , Grousilliers H. Des
Published: May 2005

Raman scattering studies of entrapped Mo(CO)6 in faujasite‐type zeolite cages, as a function of zeolite type and temperature, evidence the intracavity electrostatic field effect and the intermolecular interactions within the zeolite framework.
Continuum resonance Raman scattering in bromine: Comparison of time‐dependent calculations with time‐independent and experimental results
Authors: Hartke Bernd
Published: May 2005

An application of time‐dependent theory to continuum resonance Raman scattering in 79Br2 is described. Calculated profiles and spectra are compared with traditional time‐independent results and experimental spectra from the literature. Similarities and differences between the time‐dependent and time‐independent methods from their theoretical derivation through different stages of results up to their explanatory power are evaluated.
Description and performance of a highly sensitive confocal Raman microspectrometer
Authors: Puppels G. J. , Colier W. , Olminkhof J. H. F. , Otto C. , de Mul F. F. M. , Greve J.
Published: May 2005

A confocal Raman microspectrometer was developed for the study of small biological objects such as single living cells and metaphase and polytene chromosomes. It employs a confocal detection scheme, well known from confocal fluorescence microscopes, in order to avoid signal contributions from the environment of the samples. The resolution is 0.45 ± 0.05 μm in the lateral direction and 1.3 ± 0.1 μm in the axial direction. The laser excitation wavelength is 660 nm. At this wavelength biological samples do not degrade in the laser radiation as was the case when laser radiation of 514.5 nm was used. The signal throughput from the sample position to the detector was optimized to the extent that in the spectral region around a 1000 cm−1 Raman shift 15% of the Raman scattered light collected by the microscope objective is detected. For signal detection a liquid nitrogen‐cooled slow‐scan CCD camera is used. Laser powers of 5–10 mW suffice to obtain high‐quality Raman spectra, with signal integration times of the order of minutes. As an example, spectra obtained from the nucleus and the cytoplasm of an intact human lymphocyte are shown.
Raman and infrared spectra of the solid chlorofluorocarbons. III–trichlorofluoromethane
Authors: LeBlanc L. M. , Anderson A.
Published: May 2005

Raman and infrared spectra of crystalline trichlorofluoromethane at temperatures between 20 and 80 K were recorded in both the lattice and internal mode regions. The lattice spectra are shown to be compatible with a non‐centrosymmetric tetragonal unit cell containing four molecules on mirror plane sites, and plausible assignments are proposed. The internal mode splittings are interpreted in terms of isotopic, crystal field, Fermi resonance and LO‐TO effects.
Resonance Raman studies of the mechanism of photoreduction of iron protoporphyrin‐IX dimethyl ester in the presence of axial ligands
Authors: Verma A. L. , Chaudhury N. K.
Published: May 2005

Resonance Raman studies of iron protoporphyrin‐IX dimethyl ester chloride [FeIII(PPDME)Cl] in the presence of biologically relevant axial ligands such as 2‐methylimidazole (2‐MeIm) and 1,2‐dimethylimidazole (1,2‐Me2Im) revealed the occurrence of photoreduction even under aerobic conditions by excitation near the Soret absorption band. A comparison of the vibrational modes sensitive to the oxidation, spin and coordination states of the photoreduced and chemically reduced forms of FeIII(PPDME)Cl confirmed that the reduction of the central iron atom in the high‐spin state takes place without any reduction of the porphyrin ring. No photoreduction is observed in pure dichloromethane solvent but trace amounts of alcohols and also some other polar solvents, which facilitate the separation of ion pairs, catalyse the process of photoreduction. From the exponential dependence of the fraction of sample reduced on the rate of photoreduction and illumination time, the rate constant for photoreduction, k−1R = 10 min, is obtained and the action spectrum of photoreduction shows a maximum coinciding with the Soret absorption band. The electron transfer from the axially ligated 2‐MeIm to iron appears to be a primary step in photoreduction. From the dependence of photoreduction on the concentration of 2‐MeIm, the ligand‐free, intermediate spin FeII (PPDME) was identified as the intermediate species formed during photoreduction.
Raman spectrum of [MgCl(THF)5] [FeCl4] · THF
Authors: Shamir Jacob , Sobota Piotr
Published: May 2005

The Raman spectrum of [MgCl(THF)5] [FeCl4] · THF includes all four Raman‐activ vibrations of the [FeCl4]− anion, thus supporting the results obtained by x‐ray analysis. On the other hand, no vibration which could be assigned to the MgCl bond has been observed, which may indicate that this bond is more likely to be ionic.
Raman microprobe spectroscopy of icing on metal surfaces
Authors: Sonwalkar Nishikant , Sunder S. Shyam , Sharma S. K.
Published: May 2005

A simple optical low‐temperature icing cell was fabricated to obtain the in situ Raman spectra of ice layers forming on metallic substrates. The icing cell is optically coupled to a micro Raman multi‐channel spectrometer. The Raman spectra of the initial ice layers show characteristics of a disordered phase resembling low‐density amorphous ice. The crystalline phase develops gradually as the thickness of the ice layer increases. The disorder in the initial ice layer may be caused primarily by the rapid thermal cooling, and appears to be independent of the type of metal substrate.
Determination of excited state potential functions from continuum resonance Raman scattering: Excitation of 79Br2 from the visible to the UV region
Authors: Strempel J. , Kiefer W.
Published: May 2005

High‐resolution polarized and depolarized resonance Raman spectra of isotopically pure molecular bromine (79Br2) with Δν = 1–5 were recorded using the argon laser lines at 501.7, 496.5, 488.0, 476.5, 457.9, 363.8, 351.1 and 333.6 nm and the Kr laser line 413.1 nm. Using a high‐sensitive CCD camera, the experimentally obtained spectra have better signal‐to‐noise ratios than some of the spectra already published. All observed spectra were also calculated using second‐order perturbation theory. The high sensitivity of resonance Raman band shapes to changes in the position of excited potential curves gives the possibility of determining the potential functions of the excited states 1II1u and 3II0+u in the energy range between 20 000 and 30 000 cm−1 very accurately. These potentials allow a satisfactory description of all observed spectra, including those of the overtones, in contrast to earlier work.
Vibrational study on ferroelectric dipoles in rochelle salt
Authors: Kanesaka Isao , Kita Hayato
Published: May 2005

Complete polarized Raman spectra in the region of OD stretchings in a partially deuterated Rochelle salt were observed at room temperature and 77 K. The spectra were analysed by comparison with calculated intensity variations, identifying some bands definitely and deducing a ferroelectric dipole with a two‐site structure, where the OD stretchings are 2520 and 2424 cm−1 at room temperature. The infrared spectra in the region of OD stretchings and also OH decoupled stretchings were observed in the temperature range 310‐20 K. One of two components in the ferroelectric dipole at 2507 cm−1 was observed even at 20 K, indicating a small energy difference between the two sites. On the other hand, no important spectral change at 2507 cm−1 was found on passing through the ferroelectric phase transition. An OH group with a two‐site structure with an energy difference of 2.4 kJ mol−1 was observed for the first time at 3536 and 3523 cm−1 at 240 K, although the corresponding OD stretching was not split. It is considered that this group is not responsible for ferroelectricity.
Barrier to asymmetric internal rotation, conformational stability, vibrational spectra and assignments, and Ab Initio calculations of n‐butane‐d0, d5 and d10
Authors: Durig J. R. , Wang Aiying , Beshir Wafaa , Little T. S.
Published: May 2005

The asymmetric torsional potential function of n‐butane has been redefined based on a combination of results obtained from experimental and theoretical calculations. From the vibrational spectra of gaseous n‐butane below 500 cm−1 the asymmetric torsional fundamentals of the more stable s‐trans and high‐energy gauche conformations of n‐butane have been assigned at 121.28 and 116.60 cm−1, respectively, each with excited states falling to lower frequencies. Additionally, from variable‐temperature studies of the Raman spectra for n‐butane‐d0 and d10, the conformational enthalpy difference has been determined to be 381 ± 41 cm−1 (1089 ± 117 cal mol−1) and 369 ± 72 cm−1 (1055 ± 206 cal mol−1), respectively. Optimized structural parameters, obtained from ab initio methods, for the s‐trans and gauche conformers have been used to allow for structural relaxation during the asymmetric internal rotation and to place constraints on the determined potential function. The resulting potential coefficients are V1 = 584 ± 7, V2 = ‐96 ± 7, V3 = 1165 ± 3, V4 = 45 ± 3, V5 = ‐3 ± 2 and V6 = ‐40 + 1 and the s‐trans to gauche, gauche to gauche and gauche to s‐trans barriers are determined to be 1274, 1370 and 891 cm−1, respectively, with an enthalpy difference between the conformers of 383 ± 17 cm−1 (1095 ± 49 cal mol−1). This potential function is consistent with a dihedral angle for the gauche conformer of 65.4°. Additionally, this potential has a ‘syn’ barrier, which is the energy difference between the s‐trans minimum and the gauche to gauche transition state, of 1753 cm−1 (5.01 kcal mol−1), which is in excellent agreement with the most recent value of 1836 cm−1 (5.25 kcal mol−1) obtained from a very high‐level ab initio calculation. In order to provide a more complete description of the normal vibrational modes of n‐butane, normal coordinate analyses have been completed for n‐butane‐d0, ‐d5 and ‐d10 based on force constants from ab initio calculations. The infrared (3500‐40 cm−1) and Raman (3500‐10 cm−1) spectra of n‐butane‐d5 and ‐d10 have been obtained and complete vibrational assignments are provided. The structural parameters, conformational stabilities, barriers to internal rotation and vibrational frequencies which have been determined experientally are compared with those obtained by ab initio methods.
Surface‐enhanced Raman scattering of adsorbates
Authors: Otto A.
Published: May 2005

This review concentrates on the electronic contribution to surface‐enhanced Raman scattering (SERS). This socalled ‘chemical effect’ is quantitatively separated from classical electromagnetic enhancement. It proceeds by increased electron‐photon coupling at an atomically rough surface and by temporary charge transfer to adsorbate orbitals. These concepts are supported by various experimental results. The model accounts for the chemical specificity and vibrational selectivity of SERS and (partly) for the ‘SERS specificity’ of various metals.
High‐sensitivity Raman spectroscopic study on surface‐pressure dependence of the structure in thin langmuir–blodgett films of dipalmitoylphosphatidylcholine
Authors: Okamura Emiko , Umemura Junzo , Takenaka Tohru
Published: May 2005

By combining a high‐sensitivity charge‐coupled device detector with the total reflection technique, Raman spectra in the CH stretching region were recorded for thin Langmuir‐Blodgett (LB) films of dipalmitoylphosphatidylcholine (DPPC) prepared at various surface pressures encompassing the plateau region of its surface pressure‐area isotherm. Surface‐pressure dependences of the lateral packing and the conformational order are discussed using the peak intensity ratio between the 2880 and 2850 cm−1 bands and that between the 2935 and 2850 cm−1 bands. The results indicate that at higher surface pressures above the plateau, the hydrocarbon chains of DPPC are tightly packed and highly oriented with the all‐trans conformation. Below the plateau, however, the chains are disordered because of the increased number of the gauche conformers. The loosely packed hydrocarbon chains observed for the LB films deposited at lower surface pressures are gradually reoriented with time to form stable and highly ordered aggregates.
Surface‐enhanced Raman scattering of the complexes of silver with adenine and dAMP
Authors: Otto C. , Hoeben F. P. , Greve J.
Published: May 2005

The behaviour of adenine and 2′‐deoxyadenosine‐5′‐monophosphate (dAMP) at positive surface potentials of a silver working electrode was investigated using surface‐enhanced Raman scattering (SERS). The use of positive potentials in the presence of adenine or dAMP leads to a rapid accumulation of an intense spectrum. It is proposed that complexes of adenine (dAMP) with silver generate the observed spectra. Adenine and dAMP can be distinguished spectroscopically due to various different complexes that can be formed for adenine and not for dAMP. The SERS spectra of the silver‐adenine complexes show broad, unresolved bands between 1200 and 1500 cm−1, while the spectra of complexes of silver with dAMP show clearly resolved bands. The formation of Ag+‐adenine complexes gives rise to a decrease in pH and must therefore be associated with deprotonation of the adenine ring system. The SERS spectra of adenine can be obtained in solutions with a pH of 3.0, 7.5 and 11.0 whereas the SERS spectra of dAMP can only be obtained at a pH of 7.5 and 11.0. The time dependence of the SERS spectra of dAMP suggests that at least two different complexes of silver with dAMP are involved. The observed spectra are completely different from the ‘classical’ SERS spectrum of adenine and dAMP. This spectrum is characterized by an intense band at 729 cm−1 (at –700 mV vs. SCE). At open loop potential, however, the spectra of the Ag‐dAMP complex change slowly to the ‘classical’ SERS spectrum of dAMP.
Resonance Raman and far‐infrared studies of n‐Bu4NI3 and n‐Bu4NBr3
Authors: Zambounis J. S. , Kamitsos E. I. , Patsis A. P. , Papavassiliou G. C.
Published: May 2005

The resonance Raman and far‐infrared spectra of n‐Bu4NI3 show the coexistence of symmetrical (C2ν) and unsymmetrical (Cs) I3 − species, which are clearly distinguished by varying the wavelength of the excitation line. Only a slight deviation from D∞h symmetry has been deduced for the Br3 − ions in n‐Bu4NB3.
Resonance CARS spectroscopy on diacetylene single crystals
Authors: Materny A. , Leuchs M. , Michelis T. , Schaschek K. , Kiefer W.
Published: May 2005

An experimental CARS set‐up for resonant solid‐state coherent spectroscopy is described. Resonance CARS spectra of one unsymmetrically (TS/FBS) and two symmetrically (TS6, FBS) substituted diacetylene monomer single crystals, with a low content of polymer, were obtained with this apparatus. Particularly, spectra of the CC and the CC stretching vibrations of the polymer chains, recorded for different pump laser frequencies, were investigated. The occurrence of broad spectral CARS features which are non‐resonant and Stokes shifted relative to other observed CARS lines is discussed.
Polarized Raman spectra of single‐crystal barium nitroprusside trihydrate, Ba[Fe(CN)5NO]·3H2O
Authors: Güida J. A. , Piro O. E. , Aymonino P. J. , Sala O.
Published: May 2005

The room‐temperature polarized Raman scattering of single‐crystal Ba [Fe(CN)5NO] · 3H2O, space group Pbcm (D, No. 57), in the 2200–10 cm−1 spectral range, and a factor group analysis of the nitroprusside anion vibrational modes are presented. The near parallelism between the anion NCFeNO axis and a crystallographic axis facilitates the interpretation of the spectra. The data obtained complement already existing IR studies and the two series of results together provide reference information for the understanding of the vibrational behaviour of the recently reported electronically excited metastable states of the anion. The Raman data confirm the existence of a relatively large correlation (Davydov) splitting between NO stretching modes due to vibrational coupling between neighbouring nitrosyl groups in the lattice.
Fourier transform Raman spectrum of polycrystalline pyrazole, vibrational assignment and ab initio calculations
Authors: Durig J. R. , Bergana M. Mamula , Zunic W. M.
Published: May 2005

The Fourier transform Raman spectrum from 100 to 3300 cm−1 of liquid and polycrystalline pyrazole, magnified image was recorded. The frequencies for several of the fundamentals are significantly different from those obtained from the Raman spectra of solutions. The data are interpreted in detail. The previous assignment of one of the out‐of‐plane fundamentals (A") for the isolated molecule is questiond. The structural parameters, fundamental vibrational frequencies and values for the force constant were obtained from ab initio Hartree–Fock gradient calculations utilizing the 3–21G basis set. These results are compared with the values of some of these physical quantities previously reported.
Raman and far‐infrared spectra of cyanamide at 20 and 90 K: Atom‐atom potentials and lattice frequencies
Authors: Torrie B. H.
Published: May 2005

The Raman and infrared spectra of cyanamide have been remeasured at lower temperatures (20 K) and higher laser powers (for the Raman). The recently obtained structure of cyanamide was used as a basis for calculations of the lattice dynamics. Standard models using atom‐atom potentials of the exp ‐ 6 form, an exponentially decaying attractive potential for the hydrogen bond and distributed dipoles on the atoms, gave good fits to the structural parameters and, with scaling, gave moderately good values for the lattice frequencies provided that it was assumed that the modes associated with librations about the long axis of the molecule were not observed.
Infrared, Raman and pre‐resonance Raman spectra of vanadyl(IV) tetraphenylporphyrin
Authors: Baran E. J. , Jubert A. H. , Ferrer E. G.
Published: May 2005

The infrared and Raman spectra of vanadyl(IV) tetraphenylporphyrin were recorded between 1600 and 200 cm−1. Assignment of most of the vibrational modes was done by comparison with other related compounds. The VN and VO metal—ligand vibrations could be clearly identified. Pre‐resonance experiments were performed, using different radiation from an argon ion laser, in the energy range between the main electronic transitions of the complex [the Soret band and the (α + β) doublet]. Analysis of the excitation profiles suggests that all the enhanced bands contribute to both the A and B terms of Albrecht's equation.
Analyse Vibrationnelle des Acides gem‐Dimethylglutarique en Solution Aqueuse. I—Acide 2,2‐Dimethylglutarique et Ses Sels de Potassium
Authors: Yolou S. , Delarbre J. L. , Maury L.
Published: May 2005

Les spectres Ramon et infrarouge de l'acide 2,2‐diméthylglutarique et de ses sels de potassium ont été analysés. Les résultats obtenus nous permettent de proposer une attribution des modes fondamentaux et de déterminer le groupe de symétrie de chaque ion ou molécule.
IR and Raman spectra of AgNO3 at low temperatures
Authors: Shen Z. X. , Sherman W. F. , Kuok M. H. , Tang S. H.
Published: May 2005

The IR spectra of AgNO3 were recorded using single‐crystal samples and polarized radiation. More detailed information was obtained than that reported in previous studies using polycrystalline samples. The very strong IR absorption bands of the ν3 and ν2 modes were studied by polarized reflection measurements. Raman spectra of AgNO3 were also recorded and used to provide supplementary data. Better assignments for the components of the fundamental modes were obtained using the polarized spectra, and some isotope and combination bands were also observed and assigned. The present data allow a better understanding of the splittings of the fundamental modes. The low‐temperature phase showed a softening of the ν3 and ν4 modes as the crystals were cooled below the transition temperature (140 K), and this suggests a limited (P, T) range of stability for this phase.
Vibrational study on phase transition in ammonium Rochelle salt
Authors: Kanesaka Isao , Kita Hayato
Published: May 2005

Polarized Raman spectra of partially deuterated ammonium Rochelle salt in the region of O—D stretchings were observed at room temperature. The O—D stretchings were assigned by reference to intensity variations in polarized spectra. The O—D stretchings and also the decoupled N—D stretchings in the infrared spectrum split into many bands below Tc. Some bands split abruptly and others gradually. The abrupt splitting is ascribed to a displacive structural change of water molecules in relation to tartrate ions which accompanies ordering at one of two NX4 + sites (X = H or D). The gradual splitting is ascribed to gradual freezing of reorientational motions at the other NX4 + site. The mechanism of the phase transition is discussed in terms of these structural changes.
Resonance Raman spectra of tris(violurate)ruthenium(II) and of mixed (violurate)bis(2,2′‐bipyridine)ruthenium(II) complexes
Authors: Constantino V. R. L. , Toma H. E. , de Oliveira L. F. C. , Santos P. S.
Published: May 2005

The existence of two independent chromophores in [Ru(bipy)2(H2V)]+, where H2V− = violurate anion and bipy = 2,2′bipyridine, was demonstrated by comparing its resonance Raman spectra with those displayed by the [Ru(H2V)3]− analogue. In the former, the electronic band at 478 nm was assigned to the Ru → H2V MLCT transition, whereas the band at 415 nm was assigned to the Ru → bipy MLCT transition. In both species a tentative assignment is proposed for the enhanced modes based on comparison with related examples from the literature.
A Raman study of the misfit layer compounds, (SnS)1.17NbS2 and (PbS)1.18 TiS2
Authors: Sourisseau C. , Cavagnat R. , Tirado J. L.
Published: May 2005

The Raman and resonance Raman spectra (850–20 cm−1) of powdered samples of the misfit layer compounds (SnS)1.17NbS2 and (PbS)1.18TiS2 at 300 K have been investigated. In partial agreement with structural data, vibrational assignments are proposed for most of the internal modes of the ‘MS’ and ‘TS2’ sublattices and the band wavenumbers are compared to those in the 2H‐NbS2 and IT‐TiS2 prototypes, in order to understand the interaction in which ‘MS’ acts as the donor part of the structure. Owing to their incommensurate modulated structures along the {ξ00} direction, characteristic Raman bands at 197 cm−1 (‘SnNbS3’) or 203 cm−1 (‘PbTiS3’), assigned to mostly TA or LA type modes, become Raman active due to a zone folding mechanism. New information about the lattice dynamics in the ‘TS2’ sublayers is thus obtained.
Resonance Raman spectra of Ru(bpz) in aqueous sulfuric acid solutions
Authors: Danzer Gerald D. , Kincaid James R.
Published: May 2005

The resonance Raman spectra of tris(2,2′‐bipyrazine)ruthenium(II) complex, Ru(bpz), were obtained in solutions of H2SO4‐H2O and 2H2SO4‐2H2O at acid concentrations between 0 and 98 wt.%. The spectral results are consistent with sequential protonation (or deuteration) of the six peripheral nitrogen atoms, the first three protons being added to separate bipyrazine ligands to form Ru(bpzH+). These findings are in agreement with the conclusions of previous studies based on electronic absorption and emission spectra.
Raman and infrared spectra of solid tribromofluoromethane
Authors: Zakhary N. M. , Schlueter S. A. , Anderson A.
Published: May 2005

Vibrational spectra of solid tribromofluoromethane at temperatures between 12 K and the melting point were obtained using Raman and infrared techniques, with special emphasis on the lattice modes. No evidence for a solid‐state phase transition was found. Lattice peaks are tentatively assigned on the basis of geometrical and intensity arguments. It is shown that the spectra are compatible with a non‐centrosymmetric unit cell containing four molecules.