bluuebunny/crossref_metadata_2025 huggingface dataset:
Depolarization dispersion of a fundamental line of a totally symmetric vibration in resonance Raman scattering
Authors: Zgierski Marek Z.
Published: May 2005

Vibronic coupling of the Herzberg‐Teller type is discussed as a possible source of the depolarization dispersion of a fundamental line of a totally symmetric vibration in resonance Raman scattering (RRS). Two cases are discussed separately. The first case concerns RRS from an electronic state that borrows part of its intensity from a non‐overlapping electronic state of different symmetry. In this case the depolarization ratio of the fundamental line for right angle scattering linearly polarized light can vary between the limits 1/8 and 3/4. The second case arises when part of the intensity is borrowed from an electronic state of the same symmetry but with a transition moment non‐parallel to that of the resonant state. Such a situation can occur in molecules with a symmetry corresponding to one of the following point groups: C1, Ci, C2, Cs, C1h, C2h, S2. In this situation the depolarization ratio ρl can vary between the limits 1/8 and. In both cases the amplitude of the variations of ρl depends on the damping constant. In the second case the value of the displacement parameter of a totally symmetric mode has a major influence on the range of change of ρl. Both cases show prominent resonance‐antiresonance coincidences between depolarization dispersions and excitation profiles, which has been previously predicted for non‐totally symmetric modes, and for molecular dimers. It is pointed out that the depolarization ratio in the preresonance region is very sensitive to vibronic coupling and can serve as a probe of such coupling.
Raman spectra of cubic Cs2NaMCI6 rare earth compounds
Authors: Haley L. V. , Koningstein J. A.
Published: May 2005

The Raman spectra of the cubic compounds Cs2NaMCl6 with (M = Eu+3, Tb+3, Er+3 and Tm+3) has been observed in the region 25 cm−1 < Δν < 300 cm−1. The experimental results are in complete agreement with the factor group analysis which predicts the four vibrational Raman active bands A1g, Eg and 2T2g. Also, the absence of electronic Raman bands is discussed.
The vibrational spectra of the metalloporphins: A normal coordinate analysis of the planar vibrations in the Cu‐chelates of porphin, porphin‐d4 (meso), 1:3:5:7‐tetramethyl porphin and 1:2:3:4:5:6:7:8‐octamethyl porphin
Authors: Sunder S. , Bernstein H. J.
Published: May 2005

Normal coordinate calculations have been carried out for all the planar vibrations of Cuporphin, Cu‐porphin‐d4 (meso), Cu‐1:2:3:4:5:6:7:8‐octamethyl porphin and Cu‐1:3:5:7‐tetramethyl porphin. A method is presented to obtain the skeleton deformation and the CC stretching force constants in large organic molecules with delocalized double bonds from the bond length values. This method enabled a satisfactory calculation of 160 observed frequencies in the resonance Raman and infrared spectra of the four Cu‐porphins by using a valance force field containing only 12 independent parameters. Assignments for some of the stronger bands in the resonance Raman spectra of heme proteins and metallo‐porphins are discussed.
An analytic model of resonance Raman scattering by a continuum
Authors: Laplante Jean Pierre , Bandrauk André D.
Published: May 2005

An analytic expression is obtained for resonant photon scattering by a molecular electronic continuum. Using the model of linear potentials, it is shown that all relevant cross‐sections reduce to the linear potential Green's function. Rayleigh and Raman scattering are examined as a function of incident photon energy and also as a function of vibrational excitation.
Study of the ν1 Raman linewidth of SO in acidic solutions
Authors: Ikawa S. , Yamada M. , Kimura M.
Published: May 2005

The ν1 Raman linewidths of SO in NH4HSO4, NH4HSO4 + HCl and H2SO4 aqueous solutions were estimated by resolving the observed bands into several components with a Voigt profile. From their concentration dependence, the rate constants of proton transfer were estimated to be 4.5 × 1011 M−1s−1 consistently for the three kinds of acidic solutions.
Experimental study on the resonance Raman effect and absorption spectrum of ClO2 in solution
Authors: Eysel H. H. , Bernstein H. J.
Published: May 2005

Chlorine dioxide dissolved in inert solvents [CCl4 and CFCl3 (Freon ll)] has been investigated by means of u.v./visual‐absorption spectroscopy and Raman‐spectroscopy. The vibrational constants for the 2B1, ground state and the2A2 excited state have been redetermined. While the ground state constants are in good agreement with gas state data, the excited state constants differ considerably from previous data. The Raman excitation profile is given for the v1 fundamental and its first harmonic in the region of excitation from 6471 Å to 4579 Å. Dispersion of the depolarization ratio (ρ = 0.16(6471 Å); ρ = 0.23(4765 Å))shows the contribution of two electronic state to the polarizability tensor. Expermental evidence is given that the decomposition of ClO2 in solution is not sensitive to vislble light.
Force constants and bond polarizability derivatives of some XY4 square‐planar type ions
Authors: Pandey A. N. , Sharma D. K. , Verma U. P. , Kumar V.
Published: May 2005

The general valence force field has been employed to evaluate force constants for some square‐planar type anions e.g. XY (X = Pd, Pt or Au; Y = Cl or Br; n = 1 or 2) and ICl. Bond polarizability derivatives, from Lippincott and Nagarajan, and Long and Plane, have been evaluated and compared with the experimental results. Theoretically determined bond orders have also been compared with experimentally estimated values.
Spectres Raman d'un Monocristal de As2O3, SO3 et Calcul du Champ de Force
Authors: Mercier R. , Sourisseau C. , Lucazeau G.
Published: May 2005

The polarized Raman spectra of a single crystal of As2O3, SO3, along with the infrared spectra of this compound in the polycrystalline state have been investigated at 30 K and 300 K in the 20–4000 cm−1 range. The dependance of the frequency shift of polar vibrations with the geometry of the Raman experiments has also been studied. An assignment in terms of symmetry species is proposed for 49 of the 51 expected active modes. A normal coordinate calculation using a valence force field has been performed for the principal vibrations (k ⋍ 0) of the crystal. The good agreement between observed and calculated frequencies shows that long range forces are negligible compared to internal valence forces. There are two different SO bonds characterized by stretching force constants of 9.1 and 5.2 mdyn Å−1 and SO bond lengths have been estimated equal to 1.44 and 1.56 Å respectively, by using an empirical correlation. The AsO stretching force constants of the OAsOAs…︁ chains and of the bonds linking As and SO4 groups are similar: 2.0 and 1.9 mdyn Å−1 respectively. Therefore the crystal is not an ionic sulphate compound.
Liaisons Métal–Métal et Spectres Raman de Préresonance du Compose Co4(CO)12
Authors: Sourisseau Claude
Published: May 2005

Raman spectra of Co4(CO)12 compound in heptane solutions have been investigated in the cobalt‐cobalt bond stretching vibrations range (250–100 cm−1). For comparison, the i.r. spectrum (300–30 cm−1) of this compound in the solid state has been recorded. Using the model of one M′M3 cage, the valence force constants of cobalt‐cobalt bonds have been calculated; the force constants are compared with those of RhRh and IrIr bonds in Rh4(CO)12 and Ir4(CO)12 clusters. The compound Co4(CO)12 has also been found to display preresonance Raman spectra when irradiated with 6471, 5145, 4965, 4880, 4579 and 4545 Å excitations. This preresonance effect has been analysed by the relative intensities measurements of the totally symmetric stretching bands.
Determination of derivatives of the polarizability anisotropy in a diatomic molecule from relative Raman intensities
Authors: Buckingham A. D. , Szabo Attila
Published: May 2005

Relative intensities of the S(J) and O(J) branch lines in the fundamental and overtone bands of the vibration‐rotation Raman spectrum of a linear molecule are shown to be capable of yielding the magnitude and sign of the first and second derivatives of the polarizability anisotropy, (α∥−α⊥)′e and (α∥−α⊥)″e in relation to the equilibrium anisotropy (α∥−α⊥)e. The theory is applied to hydrogen and nitrogen.
Resonance Raman scattering from triply degenerate singlet electronic states
Authors: Pawlikowski M. , Zgierski M. Z.
Published: May 2005

Excitation profiles and depolarization dispersion curves for e and t vibrations that are active in the T × e and T × t Jahn‐Teller coupling for molecules with a non‐degenerate electronic ground state are discussed.
Raman study of the rotational isomers of bicyclopropyl and vinylcyclopropane
Authors: Salares V. R. , Murphy W. F. , Bernstein H. J.
Published: May 2005

The Raman spectra of bicyclopropyl and vinylcyclopropane were studied in the solid, liquid and vapor phases in an attempt to identify their rotational isomers and to measure their enthalpy differences. For bicyclopropyl, the presence of the s‐trans and gauche isomers in the liquid and vapor phases has been confirmed. The present measurements show that the gauche isomer is more stable in both the vapor and liquid, by 91±28 cal mol−1 in the vapor and by 188±10 cal mol−1 in the liquid. For vinylcyclopropane, features due to only two conformers could be identified in the liquid and vapor spectra. In the vapor the predominant isomer, previously identified as the s‐trans rotamer,9 was found to be more stable by 1.1±0.1 kcal mol−1.
The pure rotational Raman spectrum of sulphur trioxide
Authors: Brassington N. J. , Edwards H. G. M. , Farwell D. W. , Long D. A. , Mansour H. R.
Published: May 2005

The pure rotational Raman spectrum of sulphur trioxide in the vapour phase at 333K has been obtained and analysed for the first time. The following rotational constants and bond length were determined:

This r0 value agrees to within the sum of one standard deviation of the experimental errors with the value obtained from an analysis of the vibration–rotational infrared spectrum of the 2ν3 band.
Spectroscopic study of monosubstituted amides. VII—low frequency Raman spectra of crystallized N‐methylacetamide
Authors: Fillaux F. , Baron M. H. , De Loze C. , Sagon G.
Published: May 2005

The Raman spectra of 10 isotopic species of polycrystalline NMA were recorded at 35 K between 6 and 200 cm−1. Below 110 cm−1 at least 8 transitions are observed which are mainly due to external modes. Bands located between 110 and 170 cm−1 show unexpected isotopic effects and are interpreted taking into account IR and NIS spectra. A new internal torsional mode around the bond is proposed. The corresponding potential function involves two minima (Δω = ± 10°) separated by a weak barrier (∼600 cal/mole) indicating a nonplanar molecular skeleton.
Raman spectra of caesium and rubidium tetrachloroaluminates in the solid state
Authors: Rubbens A. , Wallart F. , Barbier P. , Mairesse G. , Wignacourt J. P.
Published: May 2005

Raman spectra of both polycrystalline samples and single crystals of CsAlCl4 and RbAlCl4 (space group Pnma (D)) have been recorded in the temperature range 298–80 K.

As for the other chloroaluminates, we find the four characteristic bands of the tetrahedral AlCl anion at 353, 128, 485–503, 180–187 cm−1 and 356, 127, 486–505 and 180–187 cm−1, respectively, for the salts CsAlCl4 and RbAlCl4. The Raman spectra of single crystals of these two compounds are similar and show that these two salts are isostructural. An assignment of the observed bands is proposed. The results are compared with those for the polyatomic cation (nitrosyl and ammonium) tetrachloroaluminates.
Normal and resonance Raman spectra of gaseous chlorine excited with an argon ion laser
Authors: Chang Hua , Hwang Dah‐Min
Published: May 2005

Normal and resonance Raman effects in gaseous chlorine were carefully studied with a powerful argon ion laser. No resonance Raman behaviour could be detected in the spectra excited by visible laser lines with wavelengths down to 4545Å. The fine structures of the normal Raman spectra were examined. Resonance Raman spectra were obtained with the 3638 and 3511 Å UV line excitation. Progressions with seven overtones were recorded. The fine structures in each overtone region were analysed and assigned as the Q and S band heads of various isotopic molecules. The Raman cross‐section was enhanced only by a factor of 1.3 in the resonance case and the integrated intensity of each overtone was about one‐third of that of the fundamental. Those two characteristics indicate that the resonance Raman term in gaseous chlorine is small in comparison with the normal Raman term even when the energy of the excitation laser line is 7593 cm−1 above the dissociation limit.
Spectroscopy study of [Ni(NH3)6]X2 compounds. III reorientational correlation times of NH3 and ClO4 groups in [Ni(NH3)6](ClO4)2
Authors: Janik B. , Janik J. M. , Janik J. A.
Published: May 2005

By applying the Raman band profile analysis method, reorientational correlation times of NH3 groups and (ClO4)− ions in [Ni(NH3)6] (ClO4)2, have been obtained. These times are of the order of psec at room temperature. They increase with decreasing temperature. NH3 reorientations do not show any significant changes when the temperature passes the phase transition region (173 K–143 K). (ClO4)− reorientations, on the other hand stop abruptly at the phase transition in 173 K. A comparison with IR and neutron scattering results leads to a choice of 120° angular jumps as the NH3 reorientational model.
Molecular reorientations and intermolecular interactions: Raman spectra of the three crystalline phases of p‐dichlorobenzene
Authors: Crafts D. L. , Bellows James C. , Prasad Paras N.
Published: May 2005

The three crystalline phases of p‐dichlorobenzene (DCB) are related to each other primarily by molecular reorientations. In order to examine the anisotropy in the crystal interactions, the effect of these molecular reorientations on the phonon dispersion and the internal vibrational exciton splitting is investigated with Raman spectroscopy. Isotopically mixed crystals (DCB‐h4:DCB‐d4) are used to measure the phonon dispersions and the vibrational exciton splittings. The results obtained show that these dynamic properties are highly sensitive to molecular reorientation, revealing an anisotropy in the crystal interactions. The anisotropy in the crystal interaction is also found to be mode selective.
Non‐enzymatic hydrolysis of acetylcholine studied by Raman spectrometry
Authors: Lautié Alain , Aslanian Dimitrina , Balkanski Minko , Merlin Jean‐Claude , Dupaix Alain
Published: May 2005

Raman spectrometry complemented by infrared spectrometry have been used to study the modifications of the acetylcholine (Ach) molecule during the course of its non‐enzymatic hydrolysis in the pH range 6 to 12. The evolution with time of Ach Raman spectra, in the 600–1800 cm−1 frequency range, has been related to the course of the reaction and the final products have been identified. The rate constant has been determined using the relative intensities of vibrations associated with the Ach molecule and with the products of the reaction. The calculated value was in agreement with the value obtained by the pH‐stat method.
Etude des systèmes SiAs‐halogènes et GeAs‐halogènes par spectrométrie Raman de gaz à haute température
Authors: Bouix Jean , Hillel Roger , Michaelides Adonis
Published: May 2005

Raman spectroscopy, because it is the most convenient method of determining the components of gaseous mixtures in equilibrium at high temperature, is well fitted for a systematic study of crystal growth mechanisms of inorganic solids by chemical transport.

We have shown that the reaction between chlorine, bromine, or iodine and solid silicon or germanium arsenide is irreversible and complete between 150 and 400 °C, resulting in the formation of arsenic and the appropriate tetrahalide of silicon or germanium. At higher temperatures the tetrahalide vapour reacts with the arsenide in excess forming arsenic and the appropriate dihalide. This equilibrium reaction effects the chemical transport. The dihalides show resonance Raman scattering involving either the symmetric stretching or bending vibration.
Raman spectroscopy with intensified vidicon detectors: A study of intact bovine lens proteins
Authors: Mathies Richard , Yu Nai‐Teng
Published: May 2005

Raman spectra of intact ocular lenses contain important structural information related to aging and cataract formation. However, the direct application of Raman spectroscopy to human eyes for cataract diagnosis has been considered unsafe because of the high laser power (∼100 mW) required to generate Raman spectra using the photomultiplier‐photon counting (PMT‐PC) detection method. The clinical application of Raman spectroscopy has become more likely with the development of sensitive multichannel optical detectors such as the ‘silicon intensified target’ (SIT) coupled to an optical multichannel analyzer (OMA). We have incorporated the SIT in a novel mismatched subtractive dispersion double monochromator that has optimum stray light (<5×10−9), throughput, and resolution for these experiments. It is demonstrated that the new SIT–OMA detection method is capable of obtaining high‐quality Raman spectra of an intact bovine lens with a laser power (∼1 mW) significantly below the threshold for retinal damage. The multichannel and photon counting detection systems have been carefully compared under high and low light level conditions so that the advantages of the SIT‐OMA system for other Raman experiments may be easily evaluated.
Resonance Raman spectra of iron(II) 2,2′‐bipyridyl complexes
Authors: Miller Philip J. , Chao Robert Shih‐Liang
Published: May 2005

The resonance Raman effect is reported for the bipyridyl ligand vibrations in the complexes {Fe(bipy)3}+2, {Fe(bipy)2(CN)2} and {Fe(bipy)(CN)4}−2. The Raman spectra were obtained using exciting laser line frequencies coincident with the visible metal–ligand charge transfer absorption bands. The identity of the resonantly enhanced Raman bands is correlated with the nature of the absorption bands. The resonantly enhanced excitation profiles of the bipyridyl vibrations are analyzed in terms of the theory of resonance Raman scattering. The results indicate that the high frequency components of these bands are primarily due to a superposition of the vibrational progressions of the symmetric ligand stretching modes and not due to additional charge transfer absorptions.
Implications of modelling the chromophore of rhodopsin and bacteriorhodopsin with resonance Raman spectra of retinal Schiff bases
Authors: Marcus Michael A. , Lemley Ann T. , Lewis Aaron
Published: May 2005

Resonance Raman spectra of protonated and unprotonated Schiff bases of all‐trans retinal with propylamine, hexylamine, butylamine, deuterated butylamine (d9), methylamine and N15 methylamine have been obtained. The spectra of methylated and deuterated butylamine Schiff bases of retinal have also been recorded. It was found that the carbon–nitrogen stretching vibration associated with the Schiff base is insensitive to changes in the mass and/or length of the saturated hydrocarbon group attached to the Schiff base except for the case of methylamine. The fingerprint region, on the other hand, is sensitive to alterations in the Schiff base substituent. Deuterating the Schiff base has a larger effect on the carbon–nitrogen stretching frequency than replacing the Schiff base nitrogen N14 with N15. Furthermore, the data on deuterated Schiff bases indicate that the CCH bending vibrational mode is altered by deuteration. Implications concerning use of these compounds for modelling visual pigments and bacteriorhodopsin are discussed.
Raman spectroscopic study of thortveitite structure silicates
Authors: Bretheau‐Raynal F. , Dalbiez J. P. , Drifford M. , Blanzat B.
Published: May 2005

Single crystals of ytterbium, lutetium and scandium pyrosilicates were grown by a floating zone technique associated with an are image furnace. The recorded infrared and Raman spectra allow complete attribution of internal and external modes, in good agreement with group theory predictions.
Laser Raman spectra of some group IB metal carbonyl cations
Authors: Neppel Anton , Hickey James P. , Butler Ian S.
Published: May 2005

The Raman spectra of [Ag(CO)2]+ and [Cu(CO)4]+ in fluorosulphonic acid at—50°C have been investigated in the CO stretching region. These data, together with previously reported infrared results, favour D∞h symmetry for the Ag(I) species and Td symmetry for the Cu(I) species. These structures are in accord with those predicted for the complexes using the valence shell electron pair repulsion (VSEPR) theory.
Resonance Raman spectra of bromine: Scattering cross‐sections for simultaneous resonance with two excited states, B3∏ (0+) and 1∏(1)
Authors: Coxon J. A. , Gramari N. , Jacon M.
Published: May 2005

This paper is concerned with the quantitative interpretation of the resonance Raman excitation profile (REP) of bromine. This is the first example of a diatomic molecule where two excited electronic states, B3∏ and 1∏, strongly intervene in the Raman tensor. The numerical calculations of all the Franck–Condon factors and densities for both excited electronic states using RKR methods are presented. The results are then applied to the calculation of the REP. This rigorous calculation is compared with an approximate method, the reflection approximation. The main properties of the REP, in particular the presence of a strong maximum on the red wing of the absorption band, are accounted for by the present theory and the contributions of the two excited electronic states are discussed.
A Raman spectroscopic study of single crystals of NaH2PO4 · 2H2O and NaD2PO4 · 2D2O
Authors: Toupry‐Krauzman N. , Poulet H. , Le Postollec M.
Published: May 2005

Polarized Raman spectra of single crystals of NaH2PO4·2H2O and NaD2PO4·2D2O have been measured as a function of temperature in the wavenumber shift range 10–3600 cm−1. Changes of phonon frequencies due to directional dispersion are found. All the observed bands have been assigned using group theory. The Raman spectra are fully consistent with the presence of strong acidic hydrogen bonds and the existence of a weakly bound water molecule.
Matrix isolation Raman spectroscopy at high pressures
Authors: Jodl H. J. , Holzapfel W. B.
Published: May 2005

A special pressure cell for Raman spectroscopy is described which contains a sample chamber with special scattering geometry and a ruby manometer for in situ pressure measurements. Typical results are given for the fundamental vibrational Raman spectra of matrix‐isolated nitrogen molecules.
Uracil and thymine monoanions in solution: Differentiation of tautomers by laser Raman spectroscopy
Authors: Lippert Bernhard
Published: May 2005

Laser Raman spectroscopy permits an identification of the N‐1 and N‐3 deprotonated tautomers of uracil and thymine and a qualitative estimation of their distribution in solution. The applicability of the method with respect to the differentiation of other heterocyclic tautomers is briefly discussed.
A practical analysis for coherent anti‐stokes Raman scattering (CARS) spectra
Authors: Fleming James W. , Johnson Charles S.
Published: May 2005

In coherent anti‐Stokes Raman scattering (CARS) spectra for condensed phases, the shape and position of an isolated line depend on the Raman cross‐section, the linewidth, the vibrational frequency and the nonresonant electronic susceptibility. Equations are presented here which relate these quantities to the measured maximum and minimum intesities and the associated frequency shifts, ωL — ωs. In the case of electronic resonance enhancement, where the Raman amplitude has real and imaginary parts, a complete analysis was obtained using the intensity Imid measured at the mid‐frequency between the extrema as the fifth known quantity. However, when the electronic susceptibility is also complex, it is a completely general result that its real and imaginary parts are mixed with those for the Raman amplitude so that only certain combinations of quantities can be obtained. Equations are also presented to correct for the interference resulting from neighboring lines. The derivations are based on perturbation theory expressions for the third‐order nonlinear susceptibility χ(3), and the results are interpreted in terms of susceptibility plots in the complex plane.
The Raman spectrum of ammonium meta‐periodate
Authors: Shurvell H. F. , Brown R. J. C. , Korppi‐Tommola J.
Published: May 2005

Raman spectra of NH4IO4 and ND4IO4 have been recorded at several temperatures between 83 K and 371 K. As the temperature is increased, several bands due to both internal and external modes of the periodate ion are shifted to lower wavenumbers. There is a crossing of the Ag and Eg librational modes of the IO4−ion near 200 K. The bands due to the ammonium ion vibrations are broadened as the temperature is increased and the librational lattice mode is no longer observable above about 200 K. The present results are correlated with observations from NQR, NMR and X‐ray diffraction studies.
Vibrational spectra and conformations of epifluorohydrin
Authors: Kalasinsky V. F. , Wurrey C. J.
Published: May 2005

The infrared and Raman spectra of solid, liquid and gaseous epifluorohydrin have been recorded. For the fluid phases, there are a number of spectral triplets which can be interpreted as arising from a cis and two nonequivalent gauche conformations. The number of bands which disappear as the solid sample is annealed indicates that a single conformation exists in the crystalline state. The temperature dependence of the intensities of Raman lines for the liquid state is consistent with enthalpy differences of approximately 0.6 and 0.4 kcal mol−1 between the most stable and each of the less stable conformers. The existence and identities of the less stable conformers are discussed.
Vibrational dephasing of the SiH stretching mode in liquid trichlorosilane
Authors: Baglin Frank Geile , Dehart Dillard L.
Published: May 2005

The Raman signal from the v1 mode of trichlorosilane has been examined by dilution in several solvents. Temperature studies were also conducted and include data from the disordered solid phase of the neat sample. The results of these studies show that (a) the v1 fundamental is involved in a dephasing process process controlled by the intramolecular potential function; (b) the neat liquid has a longer dephasing time than in any of the solvents, indicating memory retention as an intermolecular process. Additionally, environmental effects (broadening) are pronounced and appear to be related to the dipole moment of the solvent. The theoretical model proposed by Rothschild1 is used to strengthen the interpretive case offered for the dephasing mechanistic process of the fundamental.
Raman spectrum of single crystals of monoclinic B‐type gadolinium sesquioxide
Authors: Zarembowitch J. , Gouteron J. , Lejus† A. M.
Published: May 2005

The Raman spectrum of a single crystal of monoclinic B‐type (C) gadolinium sesquioxide is presented. The low temperature polarization studies allowed the unambiguous attribution of 20 among the 21 normal modes expected according to the C2h factor group analysis predictions.
The origin of intense Raman spectra from pyridine at silver electrode surfaces: The role of surface carbon
Authors: Howard Martin W. , Cooney Ralph P. , McQuillan A. James
Published: May 2005

Intense Raman spectra from pyridine at polished silver electrode surfaces, subjected to a single anodic cycle, appear to be associated with pyridine adsorption in graphitic carbon overlayers on the silver surface. This interpretation is based on the absence of pyridine line enhancement for ‘clean’ (or carbon‐free) systems and the simultaneous appearance of intense pyridine and carbon spectra for the systems subjected to a single anodic cycle. Features arising from surface carbon are evident in spectra reported by earlier authors. The evidence for the presence of carbon is based firstly on the conversion of the species in question to hydrocarbons at reducing potentials and secondly on similarities in the spectra of the systems: Ag/0.1 M KCl, Ag/0.1 M KF and Ag/0.1 M KCl, pyridine, in the region of the D and G modes of graphite (1200–1700 cm−1). Similar intensity–potential curves for the pyridine line at 1008 cm−1 and the carbon band at 1595 cm−1 indicate a surface association between these two species. The stability of the pyridine species generating the 1008 cm−1 line on a dry electrode surface favours intercalation (internal adsorption) rather than external physical electrosorption on carbon. The line at 1025 cm−1 is assigned to a silver(I) pyridine complex.
Raman spectra and crystal structure of polycrystalline tetramethylammonium salts
Authors: Kabisch G.
Published: May 2005

The Raman spectra of eight polycrystalline Me4N+ salts have been measured and are discussed in relation to crystal structures. In most of the salts, several degenerate bands of the cation show splittings due to site symmetries lower than Td. From the spectral shapes in the methyl deformation and stretching region and the intensity ratio of the two NC4 skeletal deformation modes, the extent of cation distortion in each particular salt can be deduced. These distortions are strongest in the halides, whereas no significant crystal field effects are found in the SnCl62− and CdCl3− salts. Anion Raman bands and frequencies of lattice modes are also reported.
The vibration‐rotation Raman spectra of 18O2, 17O18O, 17O2 and 16O2
Authors: Edwards H. G. M. , Long D. A. , Najm K. A. B. , Thomsen M.
Published: May 2005

The vibration‐rotation Raman spectra of the oxygen species 18O2, 17O18O, 17O2 and 16O2 have been recorded and analysed; the spectra of the 17O18O and 17O2 species are reported for the first time. The B0 and α values from these analyses were used to calculate values for the equilibrium‐state rotational constants, Be, and hence the bond lengths, re. The following values were obtained:
equation image
Linear wave‐vector dependence of zone center optical phonons
Authors: Bizek Hana M. , Imaino W. , Ramdas A. K. , Rodriguez S.
Published: May 2005

Symmetry arguments including time reversal show that the polar, degenerate optical zone center phonons exhibit a dispersion linear in wave‐vector provided the crystal does not possess improper symmetry operations. After reviewing the theory, we present experimental results on the Raman spectra of α‐quartz and bismuth germanium oxide which illustrate this effect.
The electron impact spectra of SO2
Authors: Vušković L. , Trajmar S.
Published: May 2005

The methods of electron impact spectroscopy were applied to gain information about the triplet states of the SO2 molecule. The present studies indicate hitherto undetected triplet excitations at around 4.9, 7.8, 9.3 and 10.5 eV. The angular distribution of the scattered electrons is consistent with a ã 1B1 assignment at 3.4 eV and also shows that triplet excitation(s) is present in the 4.4 eV (Ã 1B1) region. The high‐energy, low‐angle spectrum yielded relative optical absorption coefficients which, when normalized to the optical data at 200 nm, agree well with previous optical measurements in the 320 to 96 nm range. In the present work the absorption coefficients were extended down to 50 nm.
The vibrational spectra of ethylene monomer and dimer in argon matrices
Authors: Cowieson D. R. , Barnes A. J. , Orville‐Thomas W. J.
Published: May 2005

Raman spectra of ethylene trapped in argon matrices are compared with the corresponding infrared data. Bands due to monomer and dimer species could be distinguished by their concentration dependence. Possible structures of the dimer are discussed.
Multiphoton absorption in direct gap solids
Authors: Mitra S. S. , Vaidyanathan A.
Published: May 2005

The two photon absorption coefficient for several alkali halides and zincblende type semiconductors has been calculated by models developed by Keldysh, Braunstein and Basov. It is shown that the Keldysh formula is closely related to Braunstein's for allowed‐allowed transitions, while Basov's formula correspond to Braunstein's formula for allowed‐forbidden transitions. A number of inprovements and corrections are pointed out. However, comparison with published experimental data show that even the best calculated values are at least an order of magnitude smaller. A more realistic model that combines the elements of second order perturbation theory and band structure calculations gives excellent agreement with experimental data on several direct gap semiconductors. The three photon absorption coefficient is treated by a third order perturbation method and compared to the results obtained by the Keldysh model.
Resonance and pre‐resonance Raman spectra of the antitumor drugs adriamycin and daunomycin
Authors: Manfait Michel , Bernard Luclen , Theophanides Theophile
Published: May 2005

Resonance and pre‐resonance Raman spectra of solids, aqueous and D2O solutions of adriamycin and daunomycin are reported. The Raman bands are due to the chromophore anthraquinone and are coupled with the first electronic π‐π* transition of the molecules. All the observed Raman bands have been assigned to vibrations of the chromophore. Resonance enhancement for most of the Raman bands has been observed in relation to the π‐π* transition. Spectra taken at different pH values show interesting Raman intensity changes owing to a shift of the π‐π* transition towards longer wavelengths. An π‐π* transition has been assigned to the shoulder near 500 nm of the absorption spectra of the molecules on the basis of the intensity changes of some Raman bands involving the carbonyl vibrations.
Laser Raman scattering and preresonance in Co(III)‐ATP complexes
Authors: Yu Nai‐Teng , Lanir A. , Werber M. M.
Published: May 2005

Interactions of cobalt(III) ion with adenosine‐5′‐triphosphate in the presence of 1,10‐phenanthroline and superoxide were studied by laser Raman spectroscopy. Striking intensity enhancement of two adenine ring vibrations at 734 and 1430 cm−1was observed upon formation of the complex Co(III)‐(phen)‐ATP‐O2−. The effect could be abolished by addition of cyanide ion to replace the superoxide ion. The spectral features were interpreted as indicating a direct binding of Co(III) to the C6‐NH2group of adenine. The interaction between Co(III) and 1,10‐phenanthroline was manifested in the frequency and intensity changes near 436 and 1064 cm−1. Raman intensities at 734, 1312, 1055 and 1430 cm−1were measured as a function of laser exciting wavelength. The gradual changes in Raman excitation profiles of ATP lines from 647.1 nm to 457.9 nm indicated the preresonance effect with a charge transfer transition between adenine and Co(III), which may lie between 300 and 400 nm as evidenced by the more dramatic enhancement of these lines with 406.7 nm excitation.
Spectra and structure of gallium compounds: V—Infrared and Raman spectra of gaseous, liquid and solid trimethylgallium
Authors: Durig J. R. , Chatterjee K. K.
Published: May 2005

The Raman spectra (50–3500 cm−1) have been recorded for gaseous, liquid and solid trimethylgallium. The infrared spectra (40–4000 cm−1) have also been recorded for trimethylgallium in the vapor and crystalline states. A complete vibrational assignment is proposed and the out‐of‐plane, GaC3 deformation is assigned to an infrared band observed at 150 cm−1 in the spectrum of the vapor. The vibrational spectrum of the solid is very simple which indicates that the molecule remains monomeric. Only one lattice mode was observed in the far infrared spectrum and none in the Raman spectrum. The spectrum of the solid can best be interpreted on the basis of C3 site symmetry with either one or two molecules per unit cell. Normal coordinate calculations for the skeletal modes have been carried out utilizing a four atom approximation.
Preresonance Raman spectroscopy of the rhodium hexabromide anion
Authors: Spoonhower John P.
Published: May 2005

Raman spectroscopy was used in structural studies of solution‐phase RhBr63− anions. The observed spectra are consistent with an octahedral ground‐state structure. Polarization measurements of the ν1(A1g) and ν2(Eg) vibrational modes support the contention of cubic symmetry. The degree of polarization of these lines is independent of laser wavelength, not unlike observations of other d6 hexahalide complexes. No resonance enhancement is observed with either T1g or T2g electronic transitions in the visible spectral region. Rather it is believed that the Raman transitions obtain intensity by way of virtual excitation of the allowed T1u electronic transition in the near‐ultraviolet portion of the spectrum.
Low frequency Raman spectra of C2H5NH+Br− as a function of pressure up to 10 kilobars
Authors: Ratcliffe C. I. , Sherman W. F. , Wilkinson G. R.
Published: May 2005

Raman spectra of a single crystal of C2H5NH3Br have been obtained at several pressures up to 10 kbar, to observe, in particular, the behaviour of the two torsional modes. Several bands show dramatic pressure shifts. The CH3 torsion shows the largest shift of all (1.918±0.039 cm−1 kbar−1), in striking contrast to the NH3+ torsion which does not shift with pressure. Threefold barriers to rotation, and their pressure dependence, have been calculated from the torsional frequencies. An explanation of the observed behaviour has been sought in terms of hard and soft regions in the lattice structure.
Raman and IR spectra of tetrachloro phosphonium salts of some tetrachlorate (MCI4−) anions
Authors: Shamir Jacob , van der Veken Benjamin J. , Herman Medard A. , Rafaeloff Rafael
Published: May 2005

Complete Raman and IR spectra were recorded for the tetrachloro phosphonium salts of tetrachloro‐aluminate, gallate, indate and ferrate. The spectra are interpreted on the basis of these complexes being of ionic structure of the general formula: PCL4+MCI4−. All the accordingly expected fundamentals have been observed and assigned.
Polarized Raman and infrared spectra of a multilayer KY (MoO4)2 crystal
Authors: Hanuza J. , Łabuda L.
Published: May 2005

Polarized Raman and IR spectra of a single KY(MoO4)2 crystal were measured in the 10–4000 cm−1 region and discussed in relation to the molecular and crystal structures. Spectroscopic data enabled us to reveal additional intermolecular interactions due to pair coupling of the molybdate tetrahedra verifying information on the crystal layer structure of double molybdates from the KLn(MoO4)2 family.
Etude par Spectrométrie Raman du Matériau Obtenu par Insertion de l'acide Sulfurique dans le Graphite
Authors: Iskander Bachir , Vast Pierre
Published: May 2005

Laser Raman spectroscopy permits the study of black graphitic materials. Intercalated compound of first stage obtained with H2SO4 will be appear to contain the ion S2O72−. The frequencies of Raman active mode E2g2 of graphite network are in good agreement with this result. The interaction between graphitic plane and this intercalated molecule is weaker than in material obtained by action of HSO3F on graphite.
Raman study of hydrogen bonding in α and β‐oxalic acid dihydrate
Authors: Ebisuzaki Y. , Angel S. M.
Published: May 2005

The effects of different hydrogen bonding configurations upon the Raman spectrum of α‐(COOH)2·2H2O, α‐(COOD)2·2D2O, β‐(COOD)2·2D2O and (COOK)2·H2O and the temperature stability of β‐ (COOD)2·2D2O are reported. The OH stretch frequencies correlate well to the changes in the hydrogen bond length and the bond angle. The band width of the stretch frequencies, however, is not related to the hydrogen bond strength. The α phase of oxalic acid dihydrate is the more stable, low temperature form and the β crystals were observed to transform to the α phase.
Raman spectra of Br3− and I3− adsorbed on zeolites
Authors: Rubim J. C. , Sala O.
Published: May 2005

The Raman spectra of Br3− and I3− adsorbed on several zeolites were investigated in order to verify a previous assignment of bands, observed in the spectra of bromine and iodine adsorbed on zeolites, to the trihalide ions formed in the zeolites.
Raman spectroscopic studies of S16O2 and S18O2 in the gas phase: Hot band assignment
Authors: Brooker M. H. , Eysel H. H.
Published: May 2005

Raman spectra have been obtained for the fundamental modes of S16O2 and S18O2 in the gaseous phase: S16O2, ν1=1151.3, ν2=518.2, ν3=1361.5; 18O2, ν1=1100.8, ν3=1318.0 cm−1. Band shapes for the isotopically different molecules are essentially identical and conform to expectations for a nearly prolate symmetric top molecule. Accurate isotopic shifts for a number of naturally abundant isotopically different molecules are reported. A weak peak shifted −3.1 cm−1 from the ν1 peaks of S16O2 and S18O2 has been assigned to the hot band transition 010→110. This assignment has been confirmed by temperature variation studies of S16O2 in CCl4 liquid.
Intensities of rotation and vibration‐rotation Raman transitions in asymmetric top molecules
Authors: Murphy William F.
Published: May 2005

The derivation of the intensities of rotation and rotation‐vibration Raman transitions for asymmetric top molecules is given, based on irreducible spherical tensor formalism. A computer program package written to calculate such intensities is described. Its use is demonstrated by reproducing the observed contours of the pure rotational band and the asymmetric stretching vibrational band in the Raman spectrum of the SO2 molecule. The polarizability tensor component ratio required to simulate the pure rotational contour is combined with literature values for mean polarizability and depolarization ratio to obtain the principal values of the SO2 polarizability tensor. A correlation of the polarizability tensor component ratio with band types is discussed for totally symmetric bands which have been reproduced using our program and those of others.
Totally symmetric progressions in resonance Raman spectra and excitation profiles
Authors: Samoc̀ Marek , Siebrand Willem , Williams Digby F. , Woolgar Eric G. , Zgierski Marek Z.
Published: May 2005

The intensity distribution in totally symmetric progressions in resonance Raman spectra and excitation profiles is re‐examined with the aim of removing remaining discrepancies between theory and experiment. New low‐temperature intensity data are reported on the permanganate ion in a perchlorate pellet. New calculations are reported on this ion as well as on β‐carotene in carbon disulfide solution. The main conclusion is that a careful consideration of lineshapes and line broadening mechanisms is required and that intensities in resonance Raman spectra must not automatically be equated in peak heights. It is shown that the remaining discrepancies in MnO4− are due to the neglect of the nontotally symmetric modes which are Jahn‐Teller active and affect the totally symmetric excitation profiles through a breakdown of the Condon approximation. The theoretical model used to analyze β‐carotene is improved by the introduction of Gaussian lineshapes associated with inhomogeneous line broadening.
Raman spectrum and torsional potential function for isoprene conformational enthalpy difference for 2‐cyclopropylpropene
Authors: Towns T. G. , Carreira L. A. , Irwin R. M.
Published: May 2005

A polarized band at 223.7 cm−1 in the vapor phase Raman spectrum of isoprene has been observed and assigned to the 2‐0 transition of the vinyl torsion originating in the s‐cis conformation. This observation has been complemented with previously reported data to afford the determination of the vinyl torsional potential function in the form

magnified image

The potential constants are (cm−1±2σ): V1=112±18; V2=2742±34; V3=294±18; and V4=−150±16. Modifications to a standard Spex model 1401 Raman spectrophotometer to allow digitization of spectra and automated operation are described in detail. The modifications have facilitated a precise deduction of the conformational enthalpy difference in both the liquid and the vapor states of 2‐cyclopropylpropene; they are, respectively, (cm−1±2σ)246±6 and 280±40. The results are discussed in terms of different mechanisms for resonance stabilization, particularly in light of a cyclopropyl group as one of the ‘conjugated’ moieties. The effect of a methine methyl‐substitution on the torsional potential function is discussed in terms of the hyperconjugation concept.
A cation dependent low frequency vibrational band in aqueous solutions of 5′‐guanosine monophosphate
Authors: Nielsen O. Faurskov , Lund P.‐A. , Petersen Steffen B.
Published: May 2005

Low frequency Raman scattering of aqueous solutions of disodium‐5′‐guanosine monophosphate (GMP), dipotassium‐5′‐GMP, NaCl and KCl are studied by construction of a quantity R(ν). A band with a maximum at 115 cm−1 is assigned to a mode from mononucleotides, associated in a manner different from normal base stacking.
Experimental detection of the missing B1 mode in CuInS2 single crystal
Authors: Joshi N. V.
Published: May 2005

The missing low frequency B1 mode in a single crystal of CuInS2 has been experimentally detected for the first time. This mode is only Raman active; however, it was activated for infrared absorption process by introducing Fe impurity. The missing mode was investigated using Fourier transform spectroscopy. The experimentally observed value (110 cm−1) is in accordance with the theoretically predicted value.
Infrared, Raman and resonance Raman investigations of methylviologen and its radical cation
Authors: Forster M. , Girling R. B. , Hester R. E.
Published: May 2005

The infrared and Raman spectra of methylviologen (1,1′‐dimethyl‐4,4′‐bipyridine dication, MV2+) have been measured from both the solid dichloride and aqueous solutions. The preresonance behaviour of MV2+ Raman bands showed that the absorption at ˜196 nm is mainly responsible for the resonance scattering process in MV2+. In the region below 1700 cm−1, nine polarized (p˜1/3) resonance Raman bands of the methylviologen radical cation, MV+, were assigned to in‐plane ring modes. Arguments are given that the chromophore of MV+ may also partially include the methyl groups. The excitation profiles of the MV+fundamentals, measured with laser wavelengths covering the range 350.6–676.4 nm, reveal three main groups of modes, each behaving differently for the excitation in this range. Modes containing largely ν(CC) ring contributions are mainly coupled with electronic transitions at ˜395, ˜605 and ˜720 nm and yield simple excitation profiles. Modes involving principally the vibrations of the N+CH3 group show complicated interference peaks in the whole range of the excitation profiles. γ(CCC) is mainly coupled with the absorption at ˜620 nm. Resonance Raman bands of the (MV+)2 dimer have been characterized through studies of the concentration dependence of the spectra.
The 2ν4 isotropic and anisotropic Raman bands of CH4
Authors: Lolck Jens‐Erik , Brodersen Svend , Robiette Alan G.
Published: May 2005

The Raman spectrum of the very weak 2ν4 band of CH4 has been recorded in the region 2460–2675 cm−1 with a spectral resolution of about 0.30 cm−1 and with two different orientations of the linearly polarized exciting light relative to the direction of observation. The two exposures are used to obtain the purely isotropic and the purely anisotropic Raman spectrum of the band. The two spectra are interpreted in terms of a model which takes explicitly into account vibrational and rotation‐vibrational interactions with other vibrational states. Using molecular constants determined primarily from infrared spectroscopy, theoretical contours are calculated which agree very satisfactorily with the experimental ones. For the isotropic spectrum it is found that two different values of the ratio between the 2ν4(A1) and the ν1 transition moment matrix elements reproduce the spectrum equally well. It is shown that the major part of the intensity in the isotropic and anisotropic Raman spectrum is borrowed from the ν1(A1) and the ν3(F2) fundamentals, respectively, through Fermi‐type interactions, and it is also shown that the 2ν4 isotropic Raman band would have been 4–6 times more intense, if the 2ν4(A1) transition moment matrix element had been negligible.