bluuebunny/crossref_metadata_2025_split huggingface dataset:
Raman study on p‐nitroaniline in channels of the molecular sieve AlPO4–5
Authors: Marlow F. , Hill W. , Caro J. , Finger G. 
Published: May 2005

AbstractZeolite‐like molecular sieves are characterized by a regularly arranged micropore system. These pores can order adsorbed molecules. The resulting guest–host composites are promising materials for spectroscopy because of the non‐random orientation of the transition matrix elements. By studying the Raman scattering of p‐nitroaniline (PNA) within a large aluminophosphate AlPO4–5 crystal, it was found that the PNA molecules are very well aligned inside the pores, forming dipole chains with intermolecular interactions as in the solid.
Raman, Pre‐resonance Raman and electronic spectra of [VO(biuret)(SO4)] · 3H2O
Authors: Jubert A. H. , Diez R. Pis , Etcheverry S. B. , Baran E. J. 
Published: May 2005

AbstractInformation on the vibrational and electronic properties of the [VO(biuret)(SO4)] · 3H2O complex was improved in order to gain a deeper insight into the characteristics of the metal–ligand bonds. Normal Raman and pre‐resonance Raman studies were performed, which allowed a better characterization of the metal–ligand modes and a thorough analysis of the electronic spectrum. The results were also compared with theoretical semi‐empirical molecular orbital calculations.
Study of the pyridine–methanol system using four‐channel Raman spectroscopy: Concentration dependence of frequencies, line widths and integrated intensities
Authors: Kreyenschmidt M. , Eysel H. H. , Asthana B. P. 
Published: May 2005

AbstractSpectra of the pyridine–methanol system were recorded in the range 300–3820 cm−1 using the technique of four‐channel Raman spectroscopy. The relative concentrations of the two components were varied in different mixtures, such that the mole fraction of pyridine, C, was 0.1, 0.2, 0.3, 0.5, 0.7, 0.8 and 0.9. The isotropic part (Iiso) of the Raman scattered intensity was recorded for all seven mixtures and for pure pyridine (C = 1.0) and pure methanol (C = 0.0) in the region 950–3820 cm−1 only, since below 950 cm−1 the isotropic part of the intensity was too weak to provide any useful information. The most important aspect of this study was the experimental determination of integrated isotropic intensities in two regions, namely 960–1080 and 2700–3650 cm−1, and the study of their variations with changing concentration of pyridine in the different mixtures. The most striking result was the observation of excess intensity over a linear concentration dependence in the region 960–1080 cm−1. The variations in frequency shifts and line width changes measured from the isotropic part of the Raman spectra of different mixtures in the region 960–1080 cm−1, and especially in the region 2700–3650 cm−1, are discussed with a view to understanding the origin of such variations.
Surface‐enhanced resonance hyper‐Raman (SERHR) spectroscopy of photochromatic molecules
Authors: Baranov A. V. , Bobovich Ya. S. , Petrov V. I. 
Published: May 2005

AbstractThe surface‐enhanced resonance Raman and surfaces enhanced hyper‐Raman (SERHR) spectra of a photochromatic indigoid dye were obtained. The influence of stationary additional lighting (AL) at the absorption bands of the photoisomers on the SERHR intensities was observed. This is connected not only with the changes in the photoisomer concentration on the silver surface under AL but also with different scattering intensities of the resonance hyper‐Raman spectra of isomers due to their different symmetries.
Raman spectra of m‐nitrobenzoic acid–Diethanolamine single crystal
Authors: Zhang Delong , Lan Guoxiang , Hu Shifen , Wang Huafu , Zheng Jinmin 
Published: May 2005

AbstractRaman spectra of m‐nitrobenzoic acid–diethanolamine single crystal in the wavenumber range 10–3500 cm−1 were recorded at room and liquid nitrogen temperatures. The internal vibrations were assigned. The Raman spectra provide evidence for the formation of hydrogen bonds in the crystal.
Relationship between atomic polarizability tensors and valence optical theories of Raman intensities
Authors: Dudev T. , Galabov B. 
Published: May 2005

AbstractThe relationships between the valence optical theory of Raman intensities and the atomic polarizability tensors model were studied. It is shown that the atomic polarizability tensors can be expressed in terms of electro‐optical parameters. The theoretical relationships derived are illustrated with a numerical example.
Raman spectra of human keratotic biopolymers: Skin, callus, hair and nail
Authors: Williams A. C. , Edwards H. G. M. , Barry B. W. 
Published: May 2005

AbstractFourier transform Raman spectra of human keratotic biopolymers were obtained. The spectra from skin stratum corneum, callus, nail and hair were fluorescence free and the samples did not degrade during analysis. Assignments consistent with the vibrational wavenumbers were made to characterize the molecular and conformational nature of the samples. The principal structural dissimilarities were in the sulphur content of tissues containing hard keratin (hair and nail) and soft keratin (stratum corneum and callus).
Analysis of processes in latex systems by Fourier transform Raman spectroscopy
Authors: Claybourn M. , Massey T. , Highcock J. , Gogna D. 
Published: May 2005

AbstractFourier transform Raman spectroscopy near‐infrared (NIR) laser excitation was used to follow an emulsion polymerization reaction involving methyl methacrylate, butyl acrylate and allyl methacrylate monomers in a water continuous phase. The effect of NIR absorption is discussed in relation to the monomers and water. For the system studied, only parts of the spectrum are shown to suffer from significant self‐absorption due to the water. Fortunately, for monitoring the polymerization reaction through the loss in the band due to the symmetric CC stretch, self‐absorption is shown not to play a significant role.
CARS studies of H2O motional narrowing in high‐pressure and high‐temperature H2ON2 mixtures
Authors: Grisch F. , Pealat M. 
Published: May 2005

AbstractCARS spectra of the ν1 band of water vapour at room temperature and 2100 K over a large pressure range (200–19 × 105 Pa) were studied experimentally and theoretically. The influence of N2 and H2O on the rotational relaxation processes of H2O in H2ON2 mixtures was investigated. Modelling of the CARS spectrum was performed using the relaxation matrix inversion procedure. Two rotational relaxation models based on energy and angular momentum transfer were tested and good agreement between experiment and theory was found for all the conditions studied. At 19 × 105 Pa and 2100 K, motional narrowing was found to be weak, allowing calculation of the CARS spectrum with the simple isolated‐line model.
Spectra and structure of silicon‐containing compounds. XVIII—Raman and infrared spectra, conformational stability, vibrational assignment, barrier to internal rotation and ab initio calculations of ethyldichlorosilane
Authors: Afifi M. S. , Guirgis Gamil A. , Mohamed Tarek A. , Herrebout W. A. , Durig J. R. 
Published: May 2005

AbstractThe Raman (3200–10 cm−1) and infrared (3200–30 cm−1) spectra were recorded for gaseous and solid phases of ethyldichlorosilane, CH3CH2SiHCl2. Additionally, the Raman spectrum of the liquid was recorded and quantitative depolarization values were obtained. In the spectra of the gas and liquid, both the trans and gauche conformers are present with the gauche conformer being the dominant rotamer at ambient temperature, but at −126°C the trans conformer dominates the spectrum. Only the trans form is present in the vibrational spectrum of the solid. In the Raman spectrum of the liquid at ambient temperature, the amount of the gauche conformer is significantly reduced compared with that present in the gas. From the relative intensities of two pairs of Raman lines of the liquid at 192/180 and 661/709 cm−1 as a function of temperature, the enthalpy difference is found to be 143 ± 17 cm−1 (408 ± 48 cal mol−1) with the trans rotamer the more stable conformer. Similar variable‐temperature studies of the infrared spectrum with the sample dissolved in liquid krypton were carried out and the value of the enthalpy difference was determined to be 61 ± 10 cm−1 (172 ± 30 cal mol−1). This value should be near the ΔH value for the Gas. The asymmetric torsion is observed at 71 cm−1 for the gauche conformer and the potential function governing the conformational interchange is estimated. The fundamenal modes of both conformers were assigned utilizing band contours, depolarization values, group frequencies and normal coordinate calculations. The SiH bond distance was determined to have values of 1.475 and 1.476 Å for the trans and gauche conformers, respectively, from the stretching wavenumbers. All of these data are compared with the corresponding quantities obtained from ab initio gradient calculations employing the RHF/3–21G, RHF/3–21G*, RHF/6–31G*, MP2/6–31G*, and/or MP2/6–31 + G* basis sets. Complete equilibrium geometries were calculated for both conformers. The results are compared with corresponding quantities obtained for some similar molecules.
Raman and far infrared spectra, structural parameters, and ab initio calculations on acetyl chloride
Authors: Durig J. R. , Davis J. F. , Guirgis G. A. 
Published: May 2005

AbstractThe Raman spectra (3100–10 cm−1) of gaseous, liquid and solid acetyl chloride (CH3CClO) and acetyl‐d3 chloride (CD3CClO) were recorded and qualitative depolarization values were obtained for the liquid. Additionally, the infrared spectra (3100–50 cm−1) of the gas and solid were recorded. A complete vibrational assignment is proposed for both isotopomers. The assignments are supported by normal coordinate calculations utilizing force constants from the ab initio calculations. The methyl torsion is observed at 162.8 cm−1 from which a threefold barrier of internal rotation of 622 cm−1 (1779 cal mol−1) is calculated. Utilizing the frequencies for the isolated CH stretching frequencies from the CHD2CClO molecule, r0 parameters of 1.093 and 1.096 Å were obtained for the CHs and CHa bond distances. The heavy atom r0 structural parameters were obtained from previously reported rotational constants from ten isotopomers. Ab initio calculations were carried out employing the RHF/3–21G*, RHF/6–31G* and MP2/6–31G* basis sets to obtain the vibrational frequencies, force constants, infrared and Raman intensities, structural parameters and barriers to internal rotation. The theoretical results were compared with the experimental quantities when appropriate.
Order‐disorder phase transition in diethylenetriammonium chlorocadmate single crystals determined by Raman spectroscopy
Authors: Jebari F. , Becker P. , Carabatos‐Nédelec C. 
Published: May 2005

AbstractThe Raman spectra of diethylenetriammonium chlorocadmate [(denH3)CdCl5] single crystals were studied in the Raman shift range from 250 to 500 cm−1 for temperatures between 10 and 428 K. A phase transition at Tc = 168 K was observed and characterized. In particular, two Raman bands were sensitive to temperature; they correspond to the torsion motions of NH3+ at 353 cm−1 and to the skeleton deformations of the (denH3)3+ cations at 336 cm−1 to which NH3+ belongs. The analysis of the NH3+ torsion mode based on an order‐disorder model allowed the determination of the activation energy U(300 K) = 0.91 kcal mol−1 The assumption of cluster fluctuations also allowed the critical exponents to be obtained for the transition δ = 0.71 and β = 0.35, the orientation correlation time τc = 0.5 × 10−12 s at 300 K and the correlation length ζ0 ≈ 13b, b being the lattice parameter. It is concluded that the skeleton deformation mode is a localized excitation coupled to jumps of the torsion mode of NH3+.
Enhanced Raman scattering from silver metal gratings coated with p‐nitrobenzoic acid films
Authors: Fujimaki H. , Suzuki Y. , Hatta A. 
Published: May 2005

AbstractThe Raman scattering from echelette silver gratings coated with p‐nitrobenzoic acid (PNBA) films was measured as a function of the angle of incidence of the exciting laser beam. It was found that on excitation of surface plasmon polaritons (SPPs) on the grating, the Raman scattering intensity of the adsorbed PNBA− species is enhanced by a factor of five compared with its intensity at off‐resonance angles of incidence. However, an enhancement of about a factor of 10 in our estimation is observed with s‐polarized radiation independent of the angle of incidence, indicating the presence of some supplementary mechanism other than the high‐field intensity of SPP in the enhancement process. No Raman bands due to PNBA were observed in the thickness range up to 50 nm.
Raman study of temperature‐induced phase transitions in lead hafnate (PbHfO3)
Authors: Sharma Shiv K. , Jayaraman A. , Chowdhury C. Pal , Wang S. Y. 
Published: May 2005

AbstractResults of a high‐temperature Raman spectroscopic investigation up to 522 K carried out at ambient pressure on an antiferroelectric PbHfO3 multi‐domain single crystal are reported. The changes in the Raman spectral features show that temperature‐induced phase transitions occur at 435 ± 1 and at 484 ± 1 K. The first transition is possibly to a tetragonal structure and the second is to the cubic perovskite phase. The behavior is consistent with the earlier x‐ray study of PbHfO3. No soft mode behavior associated with the transitions was detected in the Raman spectra of PbHfO3. The changes observed in the high‐temperature Raman spectra of PbHfO3 are similar to those found in the spectra of isostructural PbZrO3.
Fourier transform Raman study of the conformers in poly(ethylene terephthalate)
Authors: Rodríguez‐Cabello J. C. , Quintanilla L. , Pastor J. M. 
Published: May 2005

AbstractFourier transform (FT) Raman spectroscopy has been proved to be an adequate technique for the study of the quantitative structural changes which take place in poly(ethylene terephthalate) on annealing. The two‐phase conformational model proposed previously in the infrared domain using photoacoustic FTIR has been extended to the Raman domain. Moreover, typical Raman spectral changes with the thermal process have been directly related to conformational rather than crystallinity changes. The correlation between the percentage of the trans isomer obtained by FT‐Raman and skin layer crystallinity values obtained by differential scanning calorimetry allows the crystalline and amorphous trans isomer contents to be obtained and their evolution with the annealing process to be followed.
Conformational equilibria for 2‐ and 3‐chlorostyrene: Raman and Fourier transform infrared spectra and ab initio calculations
Authors: Ribeiro‐Claro P. J. A. , Teixeira‐Dias J. J. C. 
Published: May 2005

AbstractAb initio SCF MO calculations at the 3–21G level and the vibrational spectra [Raman and Fourier transform (FT) IR] of liquid‐phase 2‐chloro‐ and 3‐chlorostyrene are reported. For 2‐chlorostyrene, the ab initio calculations predict skew and gauche minima, with an energy difference of 11.5 kJ mol−1, and no evidence of more than one conformer was found in the liquid‐phase Raman and FTIR spectra. The Raman spectra of liquid 3‐chlorostyrene show pairs of bands whose temperature‐dependent intensities clearly suggest the occurrence of a conformational equilibrium. From these bands, assigned to non‐planar cis and trans conformers, a trans–cis energy difference of 2.3 ± 0.5 kJ mol−1 was obtained for the liquid phase.
Vibrational spectrum of liquid nitromethane revisited using polarization‐sensitive coherent anti‐stokes Raman scattering (PCARS) spectroscopy
Authors: Shkurinov Alexander , Jonusauskas Gediminas , Rullière Claude 
Published: May 2005

AbstractPolarization‐sensitive coherent anti‐Stokes Raman scattering (PCARS) spectroscopy was applied for the first time for detailed analyses of vibrational resonances of neat liquid nitromethane in the spectral range 900–1500 cm−1. The polarization PCARS properties show that the main totally symmetric band ν4 at 917 cm−1 and its observed asymmetry on the lower wavenumber side (previously assigned to hot bands) are in fact two different bands. The origin of this observed asymmetry in the lower wavenumber side of the totally symmetric vibrational mode ν4 is then discussed. Spectroscopic parameters (wavenumbers, bandwidth, polarization ratio, etc.) of vibrational spectra are then determined precisely for complex spectral bands of neat liquid nitromethane taking into account unique PCARS properties.
Vibrational study of superionic phase transitions in the mixed alkali acid sulphate Cs0.5Rb0.5HSO4
Authors: Abid Y. , Mhiri T. 
Published: May 2005

AbstractRaman spectra (10–1100 cm−1) of polycrystalline samples of Cs0.5Rb0.5HSO4 were studied at temperatures ranging from 300 to 500 K. An assignment of most of the observed band is proposed. The first‐order phase transitions previously detected at 350 and 405 K were characterized:

These transitions are believed to be governed by librarians of the SO ion and the SOH stretching mode. The I→II transition is characterized by the conversion of infinite (HSO4−)n chains to cyclic (HSO4−)2 dimers. The superionic II → III transition corresponds to the weakening of SO…︁H…︁OS hydrogen bonds and to the melting of the proton sublattice to a quasi‐liquid state where proton and SO ions contribute to the unusual high conductivity. The activation energy associated with the oscillation of the proton between two SO groups is E0 = 12.1 kJ mol−1. This was extracted from the plot of Δν1/2 vs. temperature for the νSOH band at 875 cm−1. It is of the same order of magnitude as that estimated from conductivity measurements.
Caesium hydrogensulphide CsS(H,D): Hydrogen bonds and disorder of the hydrogensulphide ions
Authors: Lutz H. D. , Beckenkamp K. , Jacobs H. , Kirchgässner R. 
Published: May 2005

AbstractIR and Raman spectra (4000–50 cm−1) of caesium hydrogensulphide and also deuterated specimens were recorded in the temperature range 6–520 K. The spectra confirm the presence of SH−…︁SH− hydrogen bonds in CsSH in contrast to other MSH compounds (M = alkali metal). The temperature evolutions of the wavenumbers and half‐widths of the SH stretching and librational modes clearly display the partly second‐order phase transitions. These are driven by thermally activated disordering of the SH− ions from the antiferroelectrically ordered low‐temperature polymorph (LTM) via a one‐dimensionally disordered middle‐temperature polymorph (MTM) to the three‐dimensionally disordered room‐temperature form (RTM) of the CsCl type. The transition temperatures between these polymorphs differ depending on the degree of deuteration, viz. 105 and 115 K and 190 and 210 K for CsSH and CsSD, respectively, owing to the greater strengths of SD−…︁SD− bonds compared with SH−…︁SH− hydrogen bonds. In the RTM, the fraction of SH− ions which form hydrogen bonds decreases with increase in temperature. The strength (νSH = 2480–2550 cm−1, rH…︁S = 275–300 pm) and geometry (H…︁SH angle ≈90°) of SH−…︁SH− hydrogen bonds is also discussed.
First‐order spatial dispersion effects in the Raman spectrum of NaClO3
Authors: Ouillon R. , Pinan Lucarre J. P. , Ranson P. 
Published: May 2005

AbstractIn cubic crystals the infrared‐active triply degenerate modes split into an LO and a doubly degenerate TO mode. For crystals with T symmetry, first‐order spatial dispersion splits the polar TO modes into a set of two circularly polarized T+ and T− modes whose frequencies have only a small separation. Using incoherent high‐resolution Raman spectroscopy (a tandem Fabry–Perot Raman double monochromator of limiting resolution 0.005 cm−1), we have measured the splitting of the low‐energy TO lattice modes in the optically active material sodium chlorate.Experiments were performed in various scattering geometries to separate the optical Raman‐active modes of different symmetries (A, E, LO and TO modes). Furthermore, the difference in the Raman response of the T+ and T− modes to left or right circularly polarized incident light was detected and analysed.We measured for the three low‐energy TO modes (77, 98 and 125 cm−1 at T = 6 K) a splitting of 0.08, 0.08 and 0.105 cm−1 respectively in a right angle geometry and 0.11, 0.11 and 0.135 cm−1 respectively in a backscattering geometry (an increase in agreement with a shift proportional to the wave vector length).
From nucleic base to polynucleotide: A vibrational analysis of the repetitive subunits involved in poly(rl) strands
Authors: Ulicny J. , Ghomi M. , Tomkova A. , Miskovsky P. , Chinsky L. , Turpin P. Y. 
Published: May 2005

AbstractUltraviolet resonance Raman spectra of inosine and its deuterated species (C8‐d, Nl‐d and C8‐, Nl‐deuterated derivatives) in aqueous solution have been collected (λexc = 257 and 281 nm) and reported in the spectral region between 400 and 1800 cm−1. The observed vibrational modes have been assigned using the Wilson GF method with an empirical harmonic valence force field and a non‐redundant set of internal co‐ordinates. This normal mode analysis is based on previous work on the vibrational assignments of the hypoxanthine nucleic base and the furanose ring with various geometries. Here the analysis has been carried out by using three different nucleoside conformations as determined from x‐ray studies of molecular crystals. The most striking features of the present work are: (i) the assignments of inosine vibrational modes are very different from those of the hypoxanthine base; (ii) the best fit between measured and calculated vibrational wavenumbers and their isotopic shifts upon selective deuteration has been obtained from inosine structures containing an N‐type sugar (C3′‐endo) associated with a low‐anti base. In addition, we have tested the reliability of the force field in the case of inosine residues involved in a canonical A‐RNA helical structure by comparing the calculated wavenumbers of the most characteristic vibrational modes with those observed in off‐ and on‐resonance Raman spectra of poly(rI).
Enhancement of Cα hydrogen vibrations in the resonance Raman spectra of amides
Authors: Jordan Trace , Spiro Thomas G. 
Published: May 2005

AbstractUltraviolet resonance Raman (UVRR) spectra of polypeptides and proteins exhibit a band at ca. 1390 cm−1 whose intensity is sensitive to helical content. The assignment of this band, designated amide S, has been contentious. To study the vibrational origin of amide S, relevant amide model compounds and their selectively deuterated iso‐topomers were synthesized. N‐Methylacetamide, N‐methylpropionamide and N‐methylisobutyramide possess a methyl, methylene and methine group, respectively, adjacent to the amide carbonyl. The UVRR spectrum of the natural abundance species show resonantly enhanced vibrational bands in the region 1350–1380 cm−1. These bands disappear on deuteration of the (C)Cα. hydrogen atoms, while the amide III modes shift up to a common position (ca. 1335 cm−1) and increase in intensity. These results suggest that amide S can be assigned to a (C)Cα hydrogen bending vibration, which acquires resonance intensity by vibrational mixing with the CN stretch of the nearby amide III mode. Variation of this mixing with the CαH/CO dihedral angle can explain the sensitivity of amide III to protein secondary structure. Additional UVRR and Fourier transform IR data reveal that (C)Cα‐deuteration has a smaller effect on the amide I, I′, II and II′ vibrational modes. Finally, it is established that UVRR spectra for NMA in H2O and D2O show an absence of torsional fundamentals or overtones. These results are interpreted as indicating an energy barrier to cxcited‐state isomerization, which argues against an alternative assignment of amide S to the amide V overtone.