bluuebunny/crossref_metadata_2025 huggingface dataset:
Theory of resonance Raman scattering by molecules subject to twisting with an application to ethylene
Authors: Siebrand Willem , Zgierski Marek Z.
Published: May 2005

Model calculations are reported on molecules such as ethylene that twist on electronic excitation. Resonance Raman spectra and excitation profiles are calculated for several pairs of torsional potentials. For a 90° twist, the resonance Raman spectra show double‐quantum torsional progressions that tend to be very long for resonance in the region of strong absorption. The Raman excitation profiles of the torsional‐mode bands resemble the absorption spectrum in that most of the intensity is found in the region of near‐vertical transitions, where the upper‐state torsional levels change from vibrational to rotational. This picture remains valid if the upper state has minima at angles other than 90° relative to the ground‐state minimum, provided that the point group symmetry of the molecule is not lower than D2 at these points; this is the case for ethylene. If, however, the minimum corresponds to a lower point group, as for asymmetrically substituted ethylenes, Raman transitions involving an odd number of quanta become allowed. For very small angles of twist (≲ 15°) such systems resemble displaced harmonic oscillators. These results are compared with recently reported resonance Raman spectra in the UV absorption region of ethylene where both π→π* and Rydberg transitions are active. The analysis suggests a new potential for torsion in the first Rydberg state.
Infrared, Raman and ultraviolet spectra and normal coordinate analysis of chlorocarbonyl isocyanate
Authors: Ulic S. E. , Della Védova C. O. , Aymonino P. J.
Published: May 2005

IR data from gaseous and matrix‐isolated chlorocarbonyl isocyanate and Raman data from the liquid were obtained. The observed features agree with the existence, proved by electron diffraction, of at least two conformers due to rotational isomerism around the CN bond. Some force constants were calculated for the planar trans (anti) conformer.
Temperature dependence of line width of SO42− modes in the Raman spectra of ammonium sulphate
Authors: Bajpai P. K. , Jain Y. S. , Bist H. D.
Published: May 2005

The temperature dependence of the Raman line width of the ν1 and ν2 modes of the SO ion in ammonium sulphate was investigated. A sudden change in the full width at half maximum intensity (FWHM) of both bands is observed at the ferroelectric transition point of the crystal. The results are explained in terms of the coupling between phonons originating from these modes and NH4+ ion pseudo‐spins. The results obtained from pseudospin–phonon coupling formulations agree satisfactorily with the experimental results. The coupling also accounts for the temperature dependence of spontaneous polarization.
Electronic, vibrational and resonance Raman spectra of the layered semiconducting compound NbS3
Authors: Sourisseau C. , Cavagnat R. , Fouassier M. , Maraval P.
Published: May 2005

The electronic (900–250 nm), infrared and Raman (600–10 cm−1) spectra of polycrystalline samples of NbS3 were investigated. A complete vibrational assignment is proposed and the band wavenumbers are compared for NbS3 and the related ZrS3 and NbS2Cl2. All the assignments have been checked by a complete valence force field calculation including intrachain, interchain and interlayer contributions. The potential energy distributions and mean square vibrational amplitudes so calculated and the values of force constants are in agreement with the two‐dimensional character of the lattice dynamics in NbS3.

In addition, an extensive resonance Raman study has been performed using various exciting radiations in the visible (676.4–457.9 nm) and near‐UV regions (363.8 and 351.1 nm). The experimental unresolved Raman excitation profiles in the contour of two low‐energy electronic transitions (λmax≈︁ 600 and 560 nm) exhibit interesting interference and exact resonance effects depending on the nature of the vibration. Taking account of multi‐state interference phenomena and inhomogeneous broadening effects, these profiles compare well with the computed ones on the assumption of weakly displaced oscillators. This allows conclusions to be drawn about the scattering mechanisms and the nature of the first electronic excited states.
Vibrational spectra of the organometallic estrogen‐receptor marker [3‐O‐(3‐hydroxypropyl)‐17β‐estradiol]‐α‐tricarbonylchromium(0) and related compounds
Authors: Butler Ian S. , Dicaire François , Cordier Christine , Top Siden , Vessieres Anne , Jaouen Gerard , Guy Herve
Published: May 2005

The IR, micro‐Raman and Fourier transform (FT) Raman spectra of 3‐O‐(3‐hydroxypropyl)‐17β‐estradiol and the two (α and β) diastereomers, produced by coordination of a Cr(CO)3 moiety to the arene A ring of the steroid, are presented. The three compounds exhibit spectra typical of arene hormonal steroids and the α‐ and β‐diastereomers can be readily distinguished from one another, especially by their FT‐Raman spectra in the CO stretching region which, unlike the corresponding micro‐Raman data, are not significantly masked by the presence of strong fluorescence backgrounds. This distinction is important since the α‐diastereomer is a useful IR estrogen‐receptor marker, whereas the β‐diastereomer is not.
Raman and infrared spectra of D‐ribose and D‐ribose 5‐phosphate
Authors: Carmona P. , Molina M.
Published: May 2005

Raman and infrared spectra were examined for D‐ribose, O‐deuterated D‐ribose, [1 – 13C]‐D‐ribose [2‐ 13C]‐D‐ribose and D‐ribose 5‐phosphate as crystalline powders and in aqueous solution. The vibrational modes are assigned on the basis of isotopic frequency shifts, depolarization ratios and relative intensities. The data are of value in testing previous assignments, some of them being revised and discussed in terms of their use in determining the structure of the ribose residue in nucleotides.
Vibrational spectra and normal coordinate analysis of some diethyl tertiary amides
Authors: Sudarshan R. , Rao G. Ramana , Chalapathi V. V.
Published: May 2005

The Raman and infrared spectra of N,N‐diethylformamide, N,N‐diethylacetamide, N,N‐diethylchloroacetamide and N,N‐diethylpropionamide were measured. Raman polarization measurements were also made. A normal coordinate analysis was carried out for N,N‐diethylformamide, N,N‐diethylacetamide and N,N‐diethylchloroacetamide using a 63‐parameter modified valence force field. The force constants were refined in an overlay least‐squares technique using vibrational frequencies of the molecules to obtain a converged set of meaningful force constants. The reliability of the force constants so obtained was tested by making a zero‐order calculation for N,N‐diethylpropionamide. The potential energy distributions and eigenvectors calculated in the process were used to make unambiguous vibrational assignments.
Raman and far‐infrared spectra of crystalline chloroiodomethane
Authors: Torrie B. H. , Prystupa D. A. , Clark J. , Taylor S. , Wong Y. W.
Published: May 2005

The lattice vibrations and internal modes of polycrystalline CH2ClI and CD2ClI have been studied as a function of temperature using Raman and far‐infrared spectroscopy. Both isotopic forms have four phases; one is plastic, one is partially ordered and the other two are fully ordered. Some aspects of the structures are discussed.
Saturation effects on ultraviolet resonance Raman intensities: Excimer/YAG laser comparison and aromatic amino acid cross‐sections
Authors: Su Chang , Wang Yang , Spiro Thomas G.
Published: May 2005

Substantial saturation effects are noted for resonance Raman (RR) bands of the aromatic residues in cytochrome c (excited at 230 nm) with an H2 Raman‐shifted YAG or a frequency‐doubled excimer‐pumped dye laser. At a given average power, saturation is much lower for excimer than for YAG excitation because of the longer pulse and higher repetition rate of the excimer laser. The signal quality at low average power is significantly higher for the excimer‐excited spectra. Ultraviolet RR cross‐sections have been redetermined for aqueous phenylalanine, tyrosine and tryptophan at a series of wavelengths from 240 to 192 nm. The excimer laser was used at 209 nm and longer wavelengths, and in addition deconvolution techniques were applied to better define the individual RR bands. These improvements led to quantitative changes in the cross‐section values from those reported previously, but the interpretation of the excitation profiles in terms of excited‐state properties of the aromatic residues remains unchanged.
Raman intensities of lattice vibrations in the 2,2′‐bipyridine crystal
Authors: Muniz‐Miranda M. , Cardini G. , Castellucci E.
Published: May 2005

The intensity of the Raman external phonons of the 2,2′‐bipyridine crystal were calculated using a published method. Two different models were used in the calculation, the oriented gas model and the local field model for polarizability. The eigenvectors used in the oriented gas model were either those of the rigid body lattice dynamics phonon energy calculation or those of the complete dynamic approach in which the mixing of the external modes with the internal torsional mode was taken into account. The molecular polarizability was obtained from the fitting of the experimental intensity of the powder spectrum starting from the polarizability of biphenyl. The overall agreement between calculated and experimental intensities of the Raman spectra corresponding to the scattering tensor elements referred to the optical indicatrix principal axes was satisfactory for all the models. A smaller standard deviation was obtained using the local field model for polarizability. This model gave better results if the interactions were split over two centres, corresponding to each of the two pyridine moieties.
Vibrational spectra of SrNa2P4O12 · 6H2O and CaNa2P4O12 · 5.5H2O
Authors: Santha N. , Nayar V. U.
Published: May 2005

IR and Raman spectra of CaNa2P4O12 · 5.5H2O and SrNa2P4O12 · 6H2O were recorded and analysed. The bands corresponding to the P4O groups and water molecules are assigned. The symmetry of the P4O ion is S4 in CaNa2P4O12 · 5.5H2O and C2h in SrNa2P4O12 · 6H2O. Three crystalloraphically independent water molecules exist in these compounds. Water II and water III form strong hydrogen bonds, in contrast to water I.
Secondary structure of the double‐stranded DNA genome of bacteriophage T7 in packaged, underpackaged and unpackaged states
Authors: Thomas George J. , Serwer Philip
Published: May 2005

Double‐stranded DNA exhibits prominent Raman bands in the spectral region 600–900 cm−1, authenticated by x‐ray crystallography as diagnostic of the macromolecular secondary structure. Since the DNA Raman fingerprint can be measured in the presence of protein, Raman spectroscopy was employed to investigate the secondary structure of dsDNA packaged within the protein coat of bacteriophage T7. Comparison of the Raman spectrum of deproteinized DNA with that of wild‐type T7 phage (52% DNA, 48% protein) reveals a packaging‐associated shift of the principal BDNA Raman marker (the band of the 825–840 cm−1 interval which is a sensitive indicator of phosphodiester geometry), without shifts of other conformation sensitive Raman markers (the bands of the 600–780 cm−1 interval which indicate sugar puckers and glycosyl torsions). The Raman marker for the protein‐free state occurs at 836 cm−1, typical of B‐form DNA of heterogeneous sequence; the marker for the packaged state occurs at 825 cm−1, characteristic of a modified B‐form DNA observed previously for specific sequences. These findings indicate different B‐form variants for dsDNA in packaged and protein‐free states. The modified B‐form secondary structure of packaged DNA is maintained when the virion is thermally burst to release the genome without removal of proteins.

Comparison of the Raman spectrum of the wild‐type T7 virion with that of a deletion mutant packaging 8.4% less DNA than wild‐type (underpackaged T7), reveals the same packaging‐associated shift of the principal B‐form marker (825 cm−1) vis‐à‐vis protein‐free DNA (836 cm−1), and additional evidence of small but significant differences between phosphodiester geometries in packaged and underpackaged states. These differences are explained by a marginally (<5%) greater proportion of non‐B backbone geometry in wild‐type T7. Both wild‐type and mutant T7 exhibit Raman markers of the C2′‐endo/anti nucleoside conformations exclusively. The results are interpreted in terms of the formation of increasing amounts of non B‐form phosphodiester geometry with increasing density of DNA packaging. The data are consistent with an excess of <5% A‐type phosphodiester geometry in packaged versus underpackaged states, and 10 ± 4% excess A‐type phosphodiester geometry in packaged versus protein‐free states. Based on Raman amide I and amide III markers, the protein structures and protein‐DNA interactions in wild‐type T7 are indistinguishable from those in the T7 deletion mutant.
Phonons and phase transitions in zirconia
Authors: Perry C. H. , Lu F. , Liu D. W. , Alzyab B.
Published: May 2005

The martensitic‐austenitic phase transition in zirconia was investigated as a function of temperature and pressure using Raman and IR spectroscopy. The frequencies and symmetries of the phonon modes corresponding to the monoclinic (M),C(4 molecules per unit cell) structure were identified at 300 K and 1 atm. The temperatureinduced transition to the tetragonal (TI),Dstructure (2 molecules per unit cell) showed thermal hysteresis (1225 ↔ 1425 K). The corresponding pressure‐induced transition at room temperature showed a pressure hysteresis (3.4 ↔ 3.95 GPa). However, the structural transition was to a different tetragonal modification (TII) withD2horC4vsymmetry with 4 molecules per unit cell.
Raman spectra, vibrational assignment, structural parameters and ab initio calculations for ethyl nitrat
Authors: Durig J. R. , Sheehan T. G.
Published: May 2005

Raman spectra (4000–10 cm−1) of gas, liquid and solid ethyl nitrate were recorded. The qualitative depolarization values were obtained from the spectrum of the liquid. A vibrational assignment for the normal modes is proposed based on depolarization values, group frequencies and normal coordinate calculations. The structures for the trans and gauche conformers have been determined from ab initio Hartree‐Fock gradient calculations using the Gaussian‐82 program with both the 3–21G and 6–31G* basis sets. From this calculation at the 6–31G* level, the energy difference between the more stable trans conformer and the higher energy gauche conformers was found to be 474 cm−1 (1.36 kcal mol−1) with a gauche dihedral angle (CCON) of 79°. The trans to gauche and gauche to gauche barriers are 990 cm−1 (2.83 kcal mol−1) and 3152 cm−1 (9.01 kcal mol−1), respectively. Barriers to internal rotation for the CH3 and NO2 groups were also obtained from ab initio calculations. For the trans conformer the values are 1304 cm−1 (3.73 kcal mol−1) and 2702 cm−1 (7.73 kcal mol−1) and for the gauche conformer they are 1161 cm−1 (3.32 kcal mol−1) and 2758 (7.89 kcal mol−1) for the CH3 and NO2 barriers, respectively. Normal coordinate calculations were also performed for both conformers utilizing force fields calculated from the 3–21G basis set which support the vibrational assignments. The results of this investigation are compared with similar data on some corresponding molecules.
Theoretical investigations of continuum resonance Raman scattering in HD+
Authors: Datta Banani , Saha Samir , Bhattacharyya S. S.
Published: May 2005

Continuum resonance Raman scattering from the heteronuclear molecular ion HD+ in the wavelength range 700–2500 Å has been treated theoretically using second‐order perturbation theory together with the Racah algebra technique. Effects of interference between the intermediate 1s σg, 2p σu and 2p πu states on the scattered intensities and depolarization ratios have been invesatigated. The intensities of the Raman lines for O‐, Q‐ and S‐branches have been calculated using the non‐thermal Franck–Condon factors for vibrational and thermal Boltzmann factors for the rotational population of HD+ and a thermal rovibrational distribution corresponding to 600 K for selected transitions. The calculated cross‐sections are found to be larger than the exprimental values for neutral diatoms.
Polarisabilités Molecularires et Polarisabilités de Liaison dans H2S et D2S
Authors: Barbès H.
Published: May 2005

La simulation des contours expérimentaux des spectres Raman de rotation pure permet d'évaluer le rapport R = αb/αa pour H2S et D2S. Les valeurs de R, des polarisabilitiés moléculaires et des polarisabilités de liaison évoluent avec la deutériation.
Raman scattering from soft modes in barium‐doped lead germanate
Authors: Hosea T. J. C.
Published: May 2005

The Raman spectrum of the soft mode and adjacent low‐frequency A TO modes in pure and barium‐doped lead germanate was measured as a function of temperature, T, through the ferroelectric‐paraelectric phase transition. The barium concentrations studied varied from 2.3 to 6.6%. The Raman spectra were analysed for all the temperatures and dopings by least‐squares fitting of a model response function. In general, the phonon line widths increase with the amount of barium doping whereas the soft frequency decreases. Both the soft optic frequency and the mode strength display Curie‐Weiss behaviour close to the Curie temperature, Tc. When they are plotted as a function of T c‐T, the various fitted soft‐mode parameters generally behave in a qualitatively similar fashion for the different specimens. However, on a quantitative basis, the agreement is less good, showing that the behaviour of the soft mode does not scale simply as Tc‐T. This may indicate that the influence of the different polarizabilities of the barium defects is important in lead germanate.
Shell model description of hyper‐Raman scattering from alkali metal halides
Authors: Vogt H.
Published: May 2005

Hyper‐Raman scattering by the zone‐centre optical phonons of alkali metal halides is described in terms of an anharmonic shell model. In order to reproduce the measured relative values of the hyper‐Raman tensor elements, three types of fourth‐order coupling parameters, representing intra‐ionic, inter‐ionic and Coulomb anharmonicities have to be taken into account. Deducing the non‐linear force constants of the short‐range inter‐ionic interactions from a Born‐Mayer potential and supplementing them by exact expressions of their Coulomb Counterparts, it is possible to determine all parameters contributing to hyper‐Raman scattering. The model also predicts the third‐harmonic generation coefficients in satisfactory agreement with experimental data.
Multiplex pure rotational coherent anti‐stokes Raman spectroscopy in a molecular beam
Authors: Bloembergen Nicolaas , Chen Kuei‐Hsien , Lü Cheng‐Zai , Mazur Eric
Published: May 2005

Pure rotational coherent anti‐Stokes Raman spectroscopy using a single broad‐band dye laser was applied to study the rotational energy distribution of molecules in a pulsed supersonic beam. The multiplex BOXCARS configuration allows the accurate determination of rotational constants and rotational temperatures, and offers many advantages over other methods. The technique was applied to calibrate the cooling effect of a pulsed molecular beam of nitrogen and to study the rotational energy distributions of infrared multiphoton‐excited ethylene.
Raman spectra and normal coordinate analysis of thirteen selectively deuterated tetramethylsilanes
Authors: Fischer D. , Klostermann K. , Oehme K.‐L.
Published: May 2005

The Raman spectra of liquid (CH3)4‐mSi(CD3)m (m = 0‐4), (CH2D)4‐nSi(CH3)n and (CHD2)4‐nSi(CD3)n (n = 0‐3) were recorded from 3200 to 50 cm−1. Normal coordinate analyses were made using both a unique internal valence force field (IVFF 1) for all 13 isotopomers and 13 slightly modified IVFF 2s for each isotopomer, including torsional modes in each case. Vibrational assignments were made using the potential energy distributions and eigenvectors in addition to the depolarization ratios, the IR spectra and the Teller‐Redlich product rule.
Effect of isotope dilution on the Fermi resonance in water
Authors: Sokołowska Anna
Published: May 2005

The additivity of the contributions of HOD, H2O and D2O to the contours of the OH and OD stretching bands was studied in a 1:1 H2O‐D2O mixture. The observed non‐additivity of contours was explained in terms of Fermi resonance changes caused by the variations in resonance intermolecular coupling parameters due to isotope dilution. The integral intensities of OH and OD bands in the mixture were additive.
Vibrational spectra of para‐disubstituted benzophenones
Authors: Volovšek Vesna , Baranović Goran , Colombo Lidija , Durig James R.
Published: May 2005

Raman (3500‐20 cm−1) and IR (4000‐80 cm−1) spectra of benzophenone and a series of its para‐disubstituted derivatives (substituents F, Cl, Br and CH3) as melts and in solution were recorded. A complete empirical assignment of the measured spectra was made and the influence of para substitution on the normal modes was investigated.
High‐pressure Raman study of CsVO3 and pressure‐induced phase transitions
Authors: Kourouklis G. A. , Jayaraman A. , Espinosa G. P. , Cooper A. S.
Published: May 2005

The pressure dependence of the Raman frequencies of cesium vanadate (CsVO3) was studied using a diamond anvil cell up to 15 GPa. From the abrupt changes in the Raman specta three pressure‐induced phase transitions are inferred at 10, 11.5 and 13 GPa. The first phase transition, at 10 GPa, is subtle but affects the VO bond length. It is believed that this transition is of the same nature as that observed in postassium and rubidium vanadates. The much higher transformation pressure in CsVO3 is attributed to the anomalous compressibility of the Cs+ ion. The second phase transition involves more drastic changes in the high‐frequency region. This is attributed to the rotations and distortions in the VO4 tetrahedra which lower the symmetry of the lattice. In the third phase transition, the appearance of broader Raman peaks and the disappearance of the chain deformation modes suggest a partial disorder in the chain structure.
Raman spectroscopy of sulphur‐containing amino acids and their derivatives adsorbed on silver
Authors: Lee Heewon , Kim Myung Soo , Suh Se Won
Published: May 2005

Surface‐enhanced Raman scattering (SERS) of sulphur‐containing amino acids and peptides (L‐cysteine, L‐cystine, L‐methionine, L‐methionylglycine and glycyl‐L‐methionine) in silver sol was investigated. The Raman signal was enhanced by a factor of about 105. In the pH range 5–11, L‐cysteine was found to absorb on the silver surface through the sulphur atom and also the carboxylate and amino groups. The changes in the SER spectrum of L‐cysteine observed on lowering the pH of the sol solution below 5 suggested that the amino group was desorbed from the surface on protonation. The SER spectrum of L‐cystine was similar to that of L‐cysteine, indicating cleavage of the SS bond on adsorption on the silver surface. L‐Methionine, L‐methionylglycine and glycyl‐L‐methionine also seemed to adsorb via the sulphur atom and also the carboxylate and amino groups in the pH range 5–9. The SER spectra of these compounds showed no concentration dependence in the ranges investigated.
Resonance Raman spectroscopy of the acid–base indicator neutral red
Authors: Bisset Alison , Dines Trevor J.
Published: May 2005

Resonance Raman spectra of the acid–base indicator neutral red and its monoprotonated and diprotonated derivatives, excited in the region of the lowest energy electronic absorption bands, are reported. The bands are assigned to vibrations of the phenazine ring system and the substituents. Measurements of the band intensities have permitted an evaluation of the geometric changes attendant upon excitation to the resonant excited state.
Relationship between resonant Raman scattering in Ag–C2H4 complexes and SERS
Authors: Brings R. , Mrozek I. , Otto A.
Published: May 2005

Concentrations less than 10−2 of silver dispersed in C2H4 matrices (ratio of Ag atoms and C2H4 molecules in the matrix) induce an absorption band in the visible range by electron transfer excitation and (with the exception of the C–H stretch vibrations) shifted Raman bands, assigned to resonant enhancement by two orders of magnitude by electron transfer in Ag–C2H4 complexes. Both phenomena are absent for Ag dispersed in C2H6. These results are analogous to the chemical specific and vibrational selective surface‐enhanced Raman scattering (SERS) of C2H4 and C2H6. The loss of the electron transfer excitation by mixing oxygen into the Ag–C2H4 matrix (as measured by Ozin et al.) corresponds to the quenching of SERS by oxygen.
Raman studies of cation–surfactant interactions in alkylpolyoxyethylene surfactant aqueous solutions
Authors: Siew Diana C. W. , Cooney Ralph P. , Taylor Michael J.
Published: May 2005

Raman studies are reported of conformational change in an alkyl polyoxyethylene non‐ionic surfactant associated with coordination to alkali and alkaline earth metal cations. This surfactant has a simpler mix of conformers (with TTT relatively unimportant) compared with non‐ionic surfactants incorporating an aromatic ring in the hydrophobic head‐group. This relatively simple conformational pattern facilitates the interpretation of the 868 cm−1 band assigned to a TGTTḠT (T, trans; G, gauche; Ḡ, gauche minus) for the OCH2CH2OCH2CH2O polyoxyethylene sequence associated with surfactant‐cation complexes. Counter anions such as halides appeared to have a negligible effect on complex formation.
Resonance Raman scattering in the case of a strong dynamic Jahn–Teller effect
Authors: Tehver I.
Published: May 2005

A method is proposed for calculating the resonance Raman excitation profiles in the case of degenerate excited electronic levels strongly coupled to non‐totally symmetric degenerate vibrations, based on the semi‐classical approach. General equations have been obtained and model calculations with the Monte Carlo method for systems of cubic symmetry have been carried out. There is a simple transform relationship between the absorption spectrum and the Raman amplitude of the non‐totally symmetric mode which prevails. All the equations obtained can also be used for pre‐resonance Raman scattering regardless of the strength of the vibronic coupling.
IR and Raman spectra of MgMoO4 · nH2O (n = 1, 5)
Authors: Isaac Mary , Santha N. , Nayar V. U.
Published: May 2005

The IR and Raman spectra of two hydrated molybdates, MgMoO4 · H2O and MgMoO4 · 5H2O, were recorded and analysed. In both the compounds, bands indicating MoO octahedral coordination are observed. Three crystallographically different water molecules exist in MgMoO4 · 5H2O. MgMoO4 · H2O exhibits weak hydrogen bonds and MgMoO4 · 5H2O hydrogen bonds of medium strength.
Raman spectroscopy of BeO at low temperatures
Authors: Devanarayanan S. , Morell G. , Katiyar R. S.
Published: May 2005

Polarized first‐order Raman spectra of BeO crystal were recorded at various temperatures to study the variations in frequencies and intensities associated with some of the phonons. At 35 K five modes were assigned to be fundamentals at 338.1 682.6, 726.7 and 1085.8 cm−1. The different scattering geometries were utilized to study the directional dependence of the dipolar phonons. Two peaks at 703.6 and 1093.7 cm−1. were the quasi‐TO and LO modes, respectively. Both the frequency and the intensity of the phonons increase with decreasing temperature. The mode at 682.6 cm−1 was examined in more detail at several temperatures.
Resonance Raman spectra of dioxygen adducts of manganese(II) porphyrins in dioxygen matrices
Authors: Weselucha‐Birczynska A. , Proniewicz L. M. , Bajdor K. , Nakamoto K.
Published: May 2005

The resonance Raman spectra of side‐on type dioxygen adducts of Mn(TMP), Mn(TPP) and Mn(OEP), where TMP, TPP and OEP denote the dianions of tetramesityl‐, tetraphenyl‐ and octaethyl‐porphines, respectively, were measured in O2‐Ar(1 : 30) matrices at ca. 15 K. The bands near 990, 710 and 430 cm−1 were assigned to ν(O2), νs(MnO) and νa(MnO), respectively, based on 16O2/18O2 isotopic shifts and normal coordinate calculations on an isosceles MnO2 moiety. Vibrational coupling between the νs (MnO) and porphyrin modes obscured the location of the former mode in the spectra of Mn(TPP)O2 and Mn(OEP)O2. The bands near 825 cm−1 which appear in all three porphyrins are shifted 34–36 cm−1 on 16O2/18O2 substitution. Evidence is presented to show that this band is due to the ν(MnO) of oxomanganese(IV) porphyrin, which was produced by photo‐cleavage of the OO bond of the dioxygen adduct. These ν(MnO) are ca. 70 cm−1 higher than those observed in acetonitrile solution. This has been attributed to the difference in the spin state; the oxomanganese(IV) porphyrins in acetonitrile solution are of high spin whereas those produced in O2‐Ar matrices are of low spin.
Surface‐enhanced Raman analysis of vitamin B complex: Quantitative detection of p‐aminobenzoic acid
Authors: Narayanan V. Anantha , Bello Job M. , Stokes David L. , Vo‐Dinh Tuan
Published: May 2005

Surface‐enhanced Raman scattering (SERS) spectra of vitamin B complex extracted in ethanol were analyzed using a silver‐coated alumina substrate. The SERS effect appears to enhance selectively the spectrum of p‐aminobenzoic acid (PABA) from among the complex constituents of the vitamin B complex tablet. A calibration graph of SERS signal intensity versus concentration of PABA was constructed for quantitative analysis. With such a graph it is possible to detect PABA down to low parts per million levels. The potential of the SERS technique in other analytical and biomedical areas is discussed.
Demonstration of low‐frequency performance and microanalysis capability of multi‐channel Raman spectroscopy with near‐infrared excitation. I
Authors: Barbillat J. , Da Silva E. , Roussel B.
Published: May 2005

The use of a liquid nitrogen‐cooled unintensified charge‐coupled device (CCD) multi‐channel array detector combined with a continuous‐wave Nd: YAG laser operating at 1064 nm and a triple grating spectrograph to obtain Raman data in the low‐frequency range down to 25 cm−1 is reported. The capabilities of near‐infrared multichannel Raman microanalysis, which permits the acquisition, with a conventional optical microscope attachment, of Raman spectra with a spatial resolution of better than a few micrometres, is also illustrated.
Comparative study of the structure of TvNPV polyhedrin and TvNPV virion protein by Raman spectroscopy
Authors: Bao Peidi , Liu Xinming , Huang Tianquan , Wu Tieqiao
Published: May 2005

Raman spectra were obtained and analysed for polyhedrin and virion protein of Trabala vishnou nuclear polyhedrosis virus (TvNPV‐P and TvNPV‐VP, respectively). It was found that the secondary structures of the protein of the two samples differ: the protein of TvNPV‐P has predominantly an α‐helical and β‐sheet structure whereas that of TvNPV‐P contains predominantly a β‐sheet content, with an α‐helix content and a lower random‐coil or β‐turn content. All tyrosyl residues in the protein of TvNPV‐P are exposed, whereas 80% of the tyrosyl residues are exposed and 20% are buried in the protein of TvNPV‐VP. The majority of the tryptophan residues in the protein of TvNPV‐VP are in a hydrophobic environment. The TvNPV‐VP has a trans‐gauche‐trans configuration of the CCSSCC linkage.
Surface‐enhanced Raman spectroscopy of pyridine and thiophenol on non‐aqueous colloidal copper
Authors: Pate J. , Leiden A. , Bozlee B. J. , Garrell R. L.
Published: May 2005

Surface‐enhanced Raman (SER) spectra of pyridine and thiophenol on a copper colloid prepared in isopropanol were obtained. Aggregation of the colloid, which occurs only slowly in the presence of adsorbates, was found to be essential to the detection of SER spectral features with excitation at 660 nm. As with aqueous copper sols, thiophenol was found to adsorb more strongly than pyridine to the copper surface. However, both adsorbates required greater concentrations in the bulk solution than for aqueous systems in order for SER features to be observed.
Fourier transform and surface‐enhanced Raman spectra of barbituric acid and of its anion
Authors: De Oliveira L. F. C. , Santos P. S. , Rubim J. C.
Published: May 2005

Fourier transform Raman spectra in the near‐IR region and surface‐enhanced Raman (SER) spectra were used to obtain the vibrational spectra of barbituric acid and its anion, since their ordinary Raman spectra cannot be obtained owing to a strong fluorescence emission. Based on the present data and literature IR data, a tentative vibrational assignment is proposed for the two species. In addition, the SER spectra of barbiturate anion adsorbed on a silver electrode in borate buffer (pH 8.4) were used to infer the geometry of adsorption, which probably involves the participation of at least one of the carbonyl groups, although a more precise definition of the geometry of adsorption depends on additional data.
Polarization measurements in near‐infrared—fourier transform spectroscopy
Authors: Hoffmann Andreas , Keller Stefan , Schrader Bernhard , Ferwerda Roeland , Van Der Maas John H.
Published: May 2005

In principle, Raman measurements provide information about vibrational frequencies and intensities. Working with polarized light provides additional information about the Raman scattering tensor components. The special conditions relating to the near‐infrared‐Fourier transform (NIR‐FT) Raman technique may preclude adaptation of some of the techniques employed for measurements with linear polarized light in ‘classical’ Raman spectroscopy in the visible range. The experimental conditions for measurements of depolarization ratios of liquids (benzene, mesitylene, p‐xylene and carbon tetrachloride) using different experimental geometries with an NIR‐FT‐Raman spectrometer were elucidated. The FT technique allows the rapid and simple determination of depolarization ratios with a quality sufficient to assign the bands to totally or non‐totally symmetric species. The possibility of determining the orientation of molecules in non‐crystalline solids is also demonstrated. Finally, the feasibility of measuring the different components of the Raman scattering tensor of a single crystal of sodium chlorate is considered.
Rotational isomers of methyl trans‐cinnamate: A Raman study
Authors: Faria M. Dulce G. , Teixeira‐Dias J. J. C. , Fausto R.
Published: May 2005

The Raman and infrared spectra of methyl trans‐cinnamate were measured as a function of temperature in the liquid and solid phases. The temperature dependence of the band intensities established the presence of two conformers in the liquid phase (the s‐cis and s‐trans forms, with CCCO dihedral angles equal to 0° and 180°, respectively; ΔH(s‐trans)‐(s‐cis) = 3.43 ± 0.84 kJ mol−1) and led to the conclusion that the thermodynamically most stable s‐cis form is the only form present in the solid.
Bond length‐Raman frequency correlations in borate crystals
Authors: Chryssikos G. D.
Published: May 2005

Correlations are established between the structural data provided by x‐ray diffraction and Raman spectroscopy on borate crystals. A linear relationship is found to be adequate to describe the bond length‐stretching frequency correlations in nine meta‐, pyro‐ and ortho‐borate crystals consisting solely of triangular borate arrangements. This result allows bond length and strength predictions for newly synthesized compounds to be made, as well as assisting in the elucidation of the influence of borate tetrahedra on the πp bonding of BO− ‘probes’ in borate crystals. A wide field of applications in the structural study of borate glasses is introduced.
Hydrogen bonding and the liquid‐to‐glass transition in propan‐1‐ and ‐2‐ol at high pressures
Authors: Yenice K. M. , Reed M. D. , Lee S. A. , Chang C. S.
Published: May 2005

The pressure dependence of the vibrational modes of propan‐1‐ and ‐2‐ol was measured by Raman spectroscopy up to 8 GPa at 300 K. Changes in the observed vibrational spectra indicate that the samples undergo a liquid‐to‐glass transition at about 4.5 GPa for propan‐2‐ol and about 5.5 GPa for propan‐1‐ol. The frequency of the O‐H stretching mode (a probe of the degree of hydrogen bonding) was found to decrease at a rate of ca −28 cm−1 GPa−1 for both propan‐1‐ and ‐2‐ol.
Surface electric field‐induced Raman spectroscopy from adsorbate and substrate modes
Authors: Krasser W. , Kojnok J. , Geurts J.
Published: May 2005

Raman spectroscopy due to electric fields at surfaces, which manifests itself as surface‐enhanced Raman scattering (SERS) from adsorbate modes, and as electric field‐induced Raman scattering (EFIRS) from substrate modes, is discussed. In SERS experiments with benzene adsorbed on small Ni/SiO2 and Pt/SiO2 clusters, using exciting radiation of different wavelengths, we observed not only very strong peaks of the normally Raman active vibrational modes but also normally infrared‐active and some inactive modes. Although the frequencies of the modes are only slightly shifted with respect to liquid benzene, the relative intensites of the Raman lines are considerably changed and in addition they are dependent on the excitation wavelength. The observation of metal‐carbon vibrations indicates a strong interaction between the adsorbate and the metal atoms. Therefore, in addition to the electric field, a metal‐molecule electronic charge transfer may be responsible for the enhancement mechanism.

EFIRS is based on the symmetry‐forbidden scattering from the longitudinal optical (LO) substrate phonon. It allows the detection of the static electric field in the surface region of semiconductor substrates, which originates from electronic band bending. By EFIRS the band bending can be monitored at surfaces and interfaces for coverages from submonolayer up to more than 100 monolayers, depending on the overlayer material. Here, the Sb/GaAs(110) interface is treated as an example. Considerable band bending dynamics is observed for overlayer thicknesses up to 100 monolayers. Simultaneous analysis of the overlayer structure by Raman scattering from the Sb vibration modes allows the interpretation of the band bending dynamics.
Surface‐enhanced Raman scattering of o‐mercaptobenzoic acid in silver sol
Authors: Lee Sang Bok , Kim Kwan , Kim Myung Soo
Published: May 2005

Surface‐enhanced Raman scattering of o‐mercaptobenzoic acid (OMBA) in silver sol was investigated. At neutral and basic pH OMBA adsorbed dissociatively on the silver surface via both its sulphur and the carboxylate group and existed as sulphidobenzoate. As the sol solution was acidified, the carboxylate group in o‐sulphidobenzoate was protonated on the silver surface while the thiolate group was present as a deprotonated ionic form. At pH 1.2, OMBA adsorbed on the silver surface exclusively via its sulphur atom as o‐sulphidobenzoic acid. As the bulk concentration of OMBA increased, the effect of favourable surface packing appeared to be more important than the pH effect in determining the surface orientation of adsorbed OMBA.
Interference effects in Raman scattering from overlayers on metals
Authors: Lenac Z. , Tomaš M. S.
Published: May 2005

A general theoretical description of Raman scattering in layered systems is presented and applied to Raman scattering from overlayers on metals. The effects of interferences and metal thickness in Raman scattering from such systems are discussed in detail. It is shown that for a thick overlayer the intensities of Raman signals decrease with decreasing metal thickness; however, for a thin overlayer they may also increase, depending on the polarization of incident and scattered light and the scattering geometry chosen. The technique of interference‐enhanced Raman scattering is also reconsidered theoretically. It is suggested that greatly enhanced signals could be obtained in those configurations in which thin sample films are embedded at prescribed positions in a transparent dielectric between a reflecting metal and a high‐index superstrate (prism).
Raman, pre‐resonance Raman and electronic spectra of iron(II) saccharinate
Authors: Jubert A. H. , Diez R. Pis , Etcheverry S. B. , Baran E. J.
Published: May 2005

The Raman spectrum of solid [Fe(Sac)2 (H2O4)] · 2H2O was recorded and assigned. Some comparisons with the spectra of the related copper(II) and nickel(II) complexes were also made. The excitation profiles of the vibrational modes that show pre‐resonance on excitation with laser lines within the electronic bands are reported. On this basis, and with the aid of a semi‐empirical extended Hückel MO calculation, the assignment of the metal—ligand vibrations and the interpretation of the electronic spectrum could be reinforced.
Effect of hydrophobic environment on the resonance Raman spectra of tryptophan residues in proteins
Authors: Efremov R. G. , Feofanov A. V. , Nabiev I. R.
Published: May 2005

The influence of environmental hydrophobicity on the UV resonance Raman spectra of tryptophan residues in proteins was studied using laser excitation at 230 nm. An increase in hydrophobicity was found to enhance the resonance Raman cross‐sections without significant changes in the frequencies and relative intensities of the Trp vibrational modes. It was shown that this effect is strong enough to be used for studies of the tryptophanyl micro‐environment in proteins. The resonance Raman cross‐section of tryptophanyl increases relative to that of N‐Ac‐Trpethyl ester by factors of 2, 3, 3, 4.4 and 1.6 for melittin, melittin incorporated into liposomes, azurin, bacteriorhodopsin and lysozyme, respectively.
Micro‐Raman spectroscopy of carbon cluster composites
Authors: Grigoryan L. S. , Bist H. D. , Sathaiah S. , Sharma S. V. , Clara H. , Majumdar A. K.
Published: May 2005

Micro‐Raman spectra were obtained with three different films and also with amorphous carbon and highly oriented pyrolytic graphite samples for comparison. The spectra of the crystallites are similar, differing mainly in frequency and line width of the major line with the position varying from 1566 to 1578 cm−1. The corresponding line for the pyrolytic graphite is at 1581 cm−1. Another difference is related to the strength of two broad background features at ca. 1350 and 1595 cm−1, evidently due to a certain amount of amorphous carbon within the spot area. In general, the spectra of the crystallites are similar to that of C70 films reported earlier.
Raman intensity of lattice vibrations in β‐Ba(OH)2 · H2O
Authors: Kanesaka Isao , Ikeda Satoshi
Published: May 2005

It is shown that the Raman intensity of translational lattice vibrations in β‐Ba(OH)2 · H2O can be explained satisfactorily in terms of bond polarizability parameters obtained from the atom dipole interaction model. The analysis was carried out on the basis of two models. Model A used only bond polarizability parameters for bond stretchings. Model B used bond polarizability parameters for bond stretchings and bond rotations, where the parameters were obtained using only three atomic or ionic polarizabilities. Model B resulted in excellent agreement with observed spectra.
Vibrational Raman spectroscopic studies of calcium oxalate monohydrate and dihydrate in lichen encrustations on renaissance frescoes
Authors: Edwards H. G. M. , Farwell D. W. , Jenkins R. , Seaward M. R. D.
Published: May 2005

Vibrational Raman spectroscopic studies of the monohydrate and dihydrate of calcium oxalate were undertaken in order to characterize these compounds in lichen encrustations which cause biodeterioration of Renaissance frescoes. Spectroscopic data from the CaC2O4 · D2O species provided an aid to the vibrational assignments and indicated that amendment to some literature assignments was necessary. Application of the results to samples of the lichen Dirina massiliensis forma sorediata encrusting certain Italian Renaissance frescoes demonstrated that it is possible to identify the monohydrate and dihydrate of calcium oxalate at a microscopic level.
UV resonance Raman spectroscopy using a quasi–continuous—wave laser developed as an industrial analytical technique
Authors: Williams K. P. J. , Klenerman D.
Published: May 2005

A resonance Raman method was developed for the study of a wide range of materials possessing UV chromophores with high sensitivity. The experimental arrangement, utilizing a low peak power yet high average power quasicontinuous‐wave laser source, permits the study of both liquid and, for the first time, solid samples. Evidence for laser‐induced sample degradation was observed from low levels of solid polycyclic aromatics dispersed in potassium chloride, but this was largely overcome by sample spinning. In addition, it was found that the Raman spectrum of individual components in a complex mixture can be selectively enhanced by a judicious choice of laser wavelength. Polyethylene and poly(vinyl chloride) were investigated and evidence for unsaturation was detected from both systems. This is attributed to the resonance enhancement of unsaturated moieties contained within the polymer.
Raman scattering study of a new laser crystal: LiCaAlF6
Authors: Daniel P. , Gesland J. Y. , Rousseau M.
Published: May 2005

The Raman spectra of the trigonal LiCaAlF6 Crystal were recorded at room temperature and 10 K. Three A1g and eight Eg Raman lines are expected according to group theory. Based on the polarized Raman spectra, symmetry assignments were made for the 11 predicted Raman‐active phonon modes. Throughout the temperature range studied, no drastic evolution of the Raman spectra was observed, which suggests that there is no structural phase transition in LiCaAlF6. Analysis of the Raman spectra was made by comparison with previous studies of several crystal fluorides such as Li2ZrF6.
Vibrational spectrum, conformational stability, barriers to internal rotation, r0 structural parameters and ab initio calculations of bromomethyl methyl ether
Authors: van der Veken B. J. , Guirgis G. A. , Liu Jian , Durig J. R.
Published: May 2005

The Raman and far‐infrared spectra at a resolution of 0.10 cm−1 of gaseous bromomethyl methyl ether, BrCH2OCH3, and three of its deuterium isotopes, d2, d3 and d5, were recorded in the 350‐50 cm−1 region. The fundamental asymmetric torsional and methyl torsional modes for the d0 molecule are extensively mixed and were observed at 176 and 130 cm−1, respectively, for the stable gauche conformer with each mode having excited states falling to lower frequency. An estimate is given for the potential function governing the asymmetric rotation. On the basis of a one‐dimensional model the barrier to internal rotation of the methyl moiety is determined to be 549 ± 8 cm−1 (1.57 ± 0.02 kcal mol−1). A complete assignment of the vibrational fundamentals for all four isotopic species observed from the infrared (3500–50 cm−1) spectra of the gas and solid and Raman (3200–10 cm−1) spectra of the gas, liquid and solid is proposed. All of these data are compared with the corresponding quantities obtained from ab initio Hartree‐Fock gradient calculations employing the STO‐3G* basis set. Additionally, complete r0 geometries were determined from the combined previously reported microwave data and CH distances determined from infrared studies along with carbon—hydrogen angles transferred from the corresponding chloride. The heavy atom structural parameters (distance in Å, angles in degrees) are r(C1Br) = 1.996 ± 0.005; r(C1O)=1.359 ± 0.005; r(C2O) = 1.433 ± BrCO = 113.7 ± 0.3; ∢ C1OC2 = 113.5 ± 0.3 and dih BrC1OC2 = 70.9 ± 0.3. All of these results are discussed and compared with the corresponding quantities obtained for some similar molecules.
Raman spectroscopic study of complex formation between phenol and propionitrile
Authors: Ng J. C. F. , Park Y. S. , Shurvell H. F.
Published: May 2005

The nitrile stretching region of binary solutions of phenol in propionitrile has been studied by means of Raman spectroscopy. The number of independently varying spectral components in this region was determined by Factor Analysis to be two. The results of Factor Analysis were supported by the observation of a pseudo‐isosbestic point. The band envelope was fitted with Lorentzian—Gaussian product functions using a non‐linear least squares procedure. The results indicate the formation of a 1:1 complex. Equilibrium constants calculated for the complex formation reaction showed a strong concentration dependence.