bluuebunny/crossref_metadata_2025 huggingface dataset:
SERS study of the conformational transition of the ordering of lipid molecules deposited on a silver electrode
Authors: Guo F. C. , Chou Y. C. , Huang W. N. , Wu Wen‐Guey
Published: May 2005

Dipalmitoylphosphatidylcholine lipid molecules adsorbed on a silver electrode were found to exhibit a conformational phase transition when investigated by means of surface‐enhanced Raman scattering. The observed order‐to‐disorder transition of the hydrocarbon chain is voltage dependent and exhibits hysteresis phenomena. It is suggested that the adsorption of lipid molecules occurs at the phosphocholine moiety and the kinetic process for the transition involves a voltage‐induced conformational change of the head group.
Vibrational spectra of indole and assignments on the basis of ab initio force fields
Authors: Majoube M. , Vergoten G.
Published: May 2005

New high‐resolution Fourier transform spectra for indole vapour and its N‐deuterated analogue and Fourier transform Raman spectra for solid indole are reported. Observed frequencies for normal modes are compared with those calculated from normal coordinate analyses carried out on the basis of ab initio force fields. The latter were calculated using the 3–21G basis set and either the theoretical optimized geometry or that given by microwave spectroscopy. The force field obtained with the optimized geometry was shown to provide and excellent approach for calculating not only frequencies but also IR and Raman intensities. Except for the NH and CH stretching modes, only one scale factor for all the in‐plane modes and another for all the out‐of‐plane modes are needed in order to bring closer the calculated and observed frequencies for indole and for eleven deuterated analogues. Assignments for each normal mode were obtained from potential energy distributions among internal coordinates. Those for normal modes corresponding, in particular, to bands observed also for the tryptophar residue are discussed in detail.
High‐pressure Raman study of methyl iodide (CH3I and CD3I) up to 12 GPa
Authors: Wu Y. H. , Sasaki S. , Shimizu H.
Published: May 2005

High‐pressure Raman spectra of liquid and crystalline CH3I and CD3I were measured up to 12 GPa at 300 K in a gasketed diamond‐anvil cell. The liquid‐solid phase transition pressures were determined as 0.9 GPa for CH3I and 0.8 GPa for CD3I. For both CH3I and CD3I, two translational and two librational modes were observed in the pressure‐induced solid phase. The frequencies of the librational modes increased rapidly with increasing pressure. The frequency of the intense ν3 mode also increased rapidly with pressure. Splitting of fundamental modes was found in the solid phase, and this behaviour is discussed in terms of crystal field effects.
Raman and infrared spectra of solid bromotrifluoromethane
Authors: Zakhary N. M. , Schlueter S. A. , Anderson A.
Published: May 2005

Raman and infrared spectra of solid bromotrifluoromethane were recorded in both the internal and lattice mode regions at temperatures between 12 K and the melting point. No evidence of a solid‐state phase transition was found. Lattice peaks were assigned on the basis of geometrical and intensity arguments, and splittings of internal modes were interpreted in terms of isotopic or crystal field effects. A non‐centrosymmetric unit cell containing four molecules was shown to be compatible with the observed spectra.
Interference effects in the intensity of coherent anti‐stokes Raman scattering in thin samples
Authors: Kukk Peeter
Published: May 2005

The interference effects on the intensity of coherent anti‐Stokes Raman scattering (CARS) in thin samples of high optical quality were shown to be determined by the interference in the sample of the four lightwaves active in this non‐linear four‐wave mixing process. In the calculation of the contrast factor in the linear and non‐linear interference spectra, the optical inhomogeneities of real samples were also taken into consideration. Theoretical equations were derived which describe well the experimentally measured CARS interference spectra of thin (0.14 mm) glass. However, in the case of thin anthracene monocrystalline flakes with optical inhomogeneities, a discrepancy between the theoretical calculations and experimental data was found.
Raman and infrared spectra of solid dibromodifluoromethane
Authors: Eix S. L. , Schlueter S. A. , Anderson A.
Published: May 2005

Raman and infrared spectra of soiid dibromodifluoromethane are reported for both the lattice and internal mode regions at temperatures between 12 K and the melting point. No evidence was found for a solid‐state phase transition. Plausible assignments of all observed spectroscopic features are suggested. The spectra are compatible with a non‐centrosymmetric unit cell containing four molecules.
Vibrational studies of the disulfide group in proteins. VII. Normal mode analysis of the Raman spectra of erabutoxin, γ‐II crystallin and immunoglobulin
Authors: Qian Weili , Krimm Samuel
Published: May 2005

Normal mode calculations have been made on the known structures of disulfide bridges in erabutoxin b, a form of γ‐II crystallin, and fragments (Fab, variable‐domain of Bence‐Jones proteins) of immunoglobulins. Previously obtained Raman spectra of these molecules are analyzed in terms of general correlations derived from normal mode calculations and also the results of calculations on these particular structures. This results in more specific conclusions about these disulfide bridge structures and their changes than was possible on the basis of previous empirical correlations.
Influence of the non‐diagonal part of the potential energy matrix in the SbC13 molecule on the results of calculating the force constants of intermolecular interaction
Authors: Kondyurin A. V. , Byelousova N. K. , Byelousova S. L. , Kozulin A. T.
Published: May 2005

Raman spectra of antimony trichloride in various phases and in crystals of complexes with naphthalene and p‐xylene were measured. Normal coordinate analyses with different approximations for the potential energy matrix of SbCl3 were performed. The frequencies of lattice modes and half‐periods of rotational librations of the SbCl3 molecule were determined. The non‐diagonal elements of the potential energy matrix of AB3 molecules (in particular SbCl3) were shown to be insensitive to the intermolecular interaction. A normal coordinate analysis for SbCl3 intramolecular vibrations can be made using as an approximation only the diagonal part of the potential energy matrix for calculating the parameters of intermolecular interaction, which significantly simplifies the calculation and gives sufficient accuracy.
Effect of homogeneous and inhomogeneous broadening on resonance CARS excitation profiles
Authors: Materny A. , Kiefer W.
Published: May 2005

The influence of broadening due to intrinsic molecule and ensemble properties (homogeneous and inhomogeneous broadening) on resonance CARS excitation profiles (CEPs) was investigated by means of a theoretical model. The non‐linear susceptibility χ(3) of a homogeneous ensemble of molecules was derived from perturbation theory using a Franck—Condon model and applying a crude Born—Oppenheimer approximation. Then it was assumed that these molecules are situated in an inhomogeneous environment which changes their electronic energies. The CARS intensity for this inhomogeneous ensemble was obtained from the homogeneous CARS intensity taking into account a distribution of energies. The influence of homogeneous and inhomogeneous broadening on CEPs was demonstrated by model calculations and compared with results obtained for resonance Raman excitation profiles. Possible applications are discussed.
Surface Raman scattering of an azo dye in acidic solutions
Authors: Xi Kang , Sharma Shiv K. , Muenow David W.
Published: May 2005

The Raman scattering of azo dye adsorbed on silver sols in acidic solution was investigated and its surfaceenhanced Raman scattering (SERS) spectra and excitation behavior are reported. It was found that different tautomeric species of the azo dye show different SERS enhancements when excited with laser on‐ and off‐resonance frequencies. These observations can be explained by a charge‐transfer model rather than an electromagnetic model.
Normal coordinate treatment of Leu5‐enkephalin in the crystal state
Authors: Lagant P. , Vergoten G. , Shi S. , Zeng G. , Aubry A. , Laureyns J.
Published: May 2005

Vibrational studies on the neuropentapeptide Leu5‐enkephalin were performed for the crystal state where different specific conformations can arise. In the present case, the peptide adopts a double fused folded conformation (β‐turn), the presence of which in the crystal state is directly related to the nature of the solvent used for its crystallization. This study completes other work relating to similar conformations of isolated molecules. It can be seen that specific interactions in the crystal state perturb to a large extent the vibrational relationships between the amide frequencies and the specific sets of dihedral angles characteristic of the particular type of turn. The tyrosyl moiety and its frequency dependence on its hydrogen bond state was especially investigated both for the Fermi resonance and the hydroxyl bending modes.
Vibrational spectra, ab initio calculations and normal coordinate analysis for 3‐methyl‐3‐vinylcyclopropene
Authors: Baranović Goran , Eckert‐Maksić Mirjana , Golić Mirta , Durig James R.
Published: May 2005

The Raman spectra (3400–10 cm−1) of liquid and solid 3‐methyl‐3‐vinylcyclopropene, C3H2(CH3)CHCH2, and its isotopomer C3D2(CH3)CHCH2 were recorded. The temperature dependence of some band intensities and qualitiative depolarization ratios show that the thermodynamically preferred conformation is s‐trans. The structural parameters and conformational stability of s‐trans and gauche rotamers were obtained from ab initio calculations by employing both 3–21G and 6–31G* basis sets. Barriers to internal rotation and fundamental vibrational frequencies were calculated utilizing the 3–21G basis set. The ab initio results are consistent with the experimentally indicated greater stability of the s‐trans relative to the gauche conformer.
Spectroscopic investigation of lattice vacancies in hexaborides
Authors: Yahia Z. , Turrell S. , Mercurio J.‐P. , Turrell G.
Published: May 2005

Raman microprobe and diffuse‐reflectance Fourier transform IR spectra of a series of seven metal hexaborides show that the basic cubic symmetry of these systems is lowered owing to lattice vacancies. The resulting wave vector is oriented along the C4 axis of the first Brillouin zone. Studies of enriched boron samples indicate that the vacancies in the B6 structure are located at boron sites.
Spectroscopic characterization and Langmuir–Blodgett monolayers of N,N′‐unsymmetrical dialkyl‐3,4:9,10‐perylenebis(dicarboximide)s
Authors: Aroca R. , Maiti A. K. , Nagao Y.
Published: May 2005

The spectroscopic characterization of N‐pentyl‐N′‐R‐unsymmetrical dialkyl‐3,4:9,10‐perylenebis(dicarboximide)s (R = CH3, C2H5 and C3H7) is reported. Langmuir monolayers of all three non‐amphiphilic molecules were successfully prepared and transferred to solid substrates. The absorption and fluorescence spectra of solutions and Langumuir–Blodgett (LB) films were studied. Vibrational fundamental frequencies were observed using surface‐enhanced resonance Raman scattering and transmission and reflection–absorption Fourier transform infrared spectroscopy. The formation of aggregates in the ground and excited states (excimer formation) is also discussed.
Spectres de Vibration et Transition de Phase des Complexes Formés Entre l'Acide Oxalique et la Pyridine
Authors: Belabbes Y. , Lautié A.
Published: May 2005

Raman and infrared spectra (4000–20 cm−1) of polycrystalline pyridine–oxalic acid complexes were investigated between 80 and 300 K and an assignment in term of group frequencies is given. The 2:2 and 2:3 compounds are spectroscopically identified and the OH…︁O and NH…︁O hydrogen bonds characterized. The spectroscopic results are consistent with crystallographic data. With the deuterated oxalic acid, only one 1:1 complex is obtained and its crystalline structure is different. From spectroscopic analysis, it is found to be built of infinite chains of hydrogenoxalate ions with strong OD…︁O hydrogen bonds (νOD about 1300 cm−1 and estimated Ro…︁o = 2.53 Å). The pyridinium moiety (C5H5ND+) forms ND…︁O hydrogen bonds characterized by a νND frequency of 2130 cm−1 and an N…︁O distance of 2.75 Å. Further, in this compound, one second‐order phase transition is observed at 235 K and the structural modifications are discussed.
Raman and far‐infrared spectra, conformational stability, barriers to internal rotation, vibrational assignment and ab initio calculations of 2‐bromo‐3‐fluoropropene
Authors: Durig D. T. , Guirgis G. A. , Zhen Mengzhang , Durig J. R.
Published: May 2005

The far‐infrared spectrum (375–30 cm−1) of gaseous 2‐bromo‐3‐fluoropropene, CH2C(CH2F)Br, was recorded at a resolution of 0.10 cm−1. The fundamental asymmetric torsional mode is observed at 112.6 cm−1 with four excited states falling to lower frequency for the s‐cis (fluorine atom eclipsing the doubel bond) conformer. For the higher energy gauche conformer, the asymmetric torsion is tentatively assigned to a very weak band at 93.0 cm−1. From these data the asymmetric torsional potential was calculated. The potential function coefficients are calculated to be V1 = 306 ± 5, V2 = −120 ± 4, V3 = 928 ± 6, V4 = 118 ± 2 and V6 = 83 ± 2 cm−1, with an enthaply difference between the more stable s‐cis and higher energy gauche conformers of 200 ± 30 cm−1 [572 ± 86 kcal mol−1 (1 kcal = 4.184 kJ)]. This function gives values of 1009 cm−1 (2.88 kcal mole−1), 1024 cm−1 (2.93 kcal mol−1) and 799 cm−1 (2.88 kcal mol−1), for the s‐cis to gauche, gauche to gauche, and gauche to s‐cis barriers, respectively. From the relative intensities of the Raman lines of the gas at 548 cm−1 (gauche) and 678 cm−1 (s‐cis) as a function of temperature, the enthalpy difference is found to be 196 ± 23 cm−1 (560 ± 66 cal mol−1), and a similar study of the liquid gives a value of 66 ± 4 cm−1 (189 ± 11 cal mol−1) with the s‐cis conformer the more stable rotamer in both of these phases. The s‐cis conformer is the rotamer present in the crystalline solid. The Raman spectrum of the gas was recorded from 3500 to 70 cm−1 and, utilizing these data and previously reported infrared data, a complete vibrational analysis is proposed for both conformers. The conformational stability, barriers to internal rotation and fundamental vibrational frequencies, which were determined experimentally, are compared with those obtained from ab initio gradient calculations employing the RHF/LANL1DZ basis set and/or this basis set with electron correlation at the MP2 level, and with the corresponding quantities for some similar molecules.
Spectroscopic characterization and Langmuir–Blodgett films of N,N‐symmetrical dialkyl‐3,4:9,10‐perylenebis(dicarboximide)s
Authors: Maiti A. K. , Aroca R. , Nagao Y.
Published: May 2005

The electronic and vibrational spectra of N‐R‐N′‐R‐symmetrical dialkyl‐3,4:9,10‐perylenebis(dicarboximide)s (R = C5H11, C6H13 and C8H17) are reported. Langmuir monolayers were prepared and surface pressure–area isotherms were measured for three non‐amphiphilic molecules. Langmuir–Blodgett (LB) films of mixed layers only were fabricated on solid substrates. Fundamental vibrational frequencies were observed using surface‐enhanced resonance Raman scattering, transmission and reflection–absorption (RAIRS) Fourier transform infrared spectroscopy. The molecular orientation in the LB films was established from the transmission and RAIRs spectra. Molecular aggregation is reduced by the presence of bulky alkyl substituents. The adsorption of electron acceptor molecules and its effect on the fluorescence yield are also reported.
Raman spectroscopic determination of boroxol and borate ring contents in lead borate glasses
Authors: Witke K. , Hübert Th. , Reich P. , Splett Ch.
Published: May 2005

Glasses in the systemxPbO·(100 –x)B2O3(0 ≤x≤ 30 mol.%) were studied by Raman spectroscopy. The conversion of boroxol rings into borate rings containing one or two BO4groups due to the transformation of threefold to fourfold coordinated boron with increasing content of lead oxide was determined from the intensities of the Raman peaks at 805 and 770 cm−1. Quantitative measurements were carried out on highly finished spherical samples to allow different reflection losses of the samples to be taken into account.
Total internal reflection Raman spectroscopy as a method to study water structure near Langmuir–Blodgett films
Authors: Nickolov Z. S. , Earnshaw J. C. , McGarvey J. J.
Published: May 2005

A single‐pass total internal reflection (TIR) Raman technique for studying the stretching modes of water close to Langmuir–Blodgett (LB) films of amphiphilic molecules is described. The method is based on efficient collection of the 458 nm (argon ion laser) excited Raman scattering from water layers adjacent to a sapphire prism coated with LB films. The experimental arrangement permitted comparison between scattering from vicinal water and that from bulk water. Polarized TIR Raman spectra for D2O of reasonable signal‐to‐noise ratio were obtained at moderate laser excitation powers (50–100 mW). However, the levels of parasitic scattering from the prism compromised the collection of corresponding spectra of good quality for H2O. Comparisons were made between the OD Raman band for D2O layers adjacent to the prism coated with LB films of ω‐tricosenoic acid with that for D2O near the uncoated prism. Small but well defined increases in the intensity of the low‐frequency shoulder of the OD band near 2400 cm−1 for the coated compared with the uncoated case are discussed in terms of possible structuring of the vicinal water by the hydrophobic film. Refinements to the experimental set‐up to increase further the sensitivity for probing water layers near surfaces are briefly considered.
Simple cell for microscale capillary solution and supercritical fluid Raman spectroscopy
Authors: Howdle Steven M. , Best Stephen P.
Published: May 2005

A microscale capillary Raman solution flow cell has been developed utilizing conventional high‐performance liquid chromatographic capillary tubing. This cell is suitable for both liquids and gases over a wide range of pressures. The introduction of a liquid flow along the capillary allows the collection of Raman spectra of intensely coloured and highly absorbing solutions, e.g. I2CCl4, using 514.5 nm excitation. The application of this cell to the examination of supercritical fluids is demonstrated. The use of small cross‐section capillary tubing (ca 10−5 cm2) allows high linear flow‐rates to be maintained with comparatively small solution volumes.
Resonance Raman spectroscopic study of polypyrrole in CuZSM‐5
Authors: Blanking James R. , Millar Graeme J. , Bowmaker Graham A. , Cooney Ralph P.
Published: May 2005

Raman spectroscopy was employed to study the polymerization of pyrrole over a selection of copper‐exhanged ZSM‐5 zeolites. No polymerization occurred on catalysts of low copper content, which suggested that a critical concentration of copper(II) cations was required for reaction. On ZSM‐5 materials with low Si/Al ratios, bands were detected which were characteristic of partially oxidized polypyrrole and monomeric pyrrole. The polymer was degraded in the presence of residual oxygen. It was shown that the polymer incorporated both aromatic‐ and quinoidal‐type structures. Further, resonance Raman spectroscopy suggested that the charge carrier present in the oxidized polymer was associated with the quinoid arrangement.
Polarized Raman and infrared studies of single crystals of orthorhombic modification of polyoxymethylene and its linear oligomer: Crystal structures and vibrational assignments
Authors: Kobayashi Masamichi , Adachi Toshihisa , Matsumoto Yoshitake , Morishita Hirofumi , Takahashi Takehito , Ute Koichi , Hatada Koichi
Published: May 2005

In order to make vibrational assignments of the metastable orthorhombic modification of polyoxymethylene (o‐POM), polarized Raman and infrared spectra of a single crystal of deca(oxymethylene) diacetate, CH3COO(CH2O)10COCH3 (POMAc10), a linear oligomer of POM, were measured and compared with previous results obtained using a micron‐sized single crystal of o‐POM. On the basis of the orientation of the o‐POM sublattice in the POMAc10 crystal, assignments of the zone‐centre modes of o‐POM was established and the unit cell orientation in the micron‐sized o‐POM single crystal was decided. The morphology‐dependent frequency shifts of the parallel infrared bands (B1 modes) in the POMAc10 crystal, which has a specific morphological structure different from the lamellar crystal of high‐molecular‐weight o‐POM, were investigated on the basis of the transition dipolar coupling theory.
Raman studies of intact and sodium doped 13C‐substituted poly‐p‐phenylene
Authors: Furukawa Yukio , Ohtsuka Hirofumi , Tasumi Mitsuo , Wataru Isao , Kanbara Takaki , Yamamoto Takakazu
Published: May 2005

The Raman and infrared spectra of 13C‐substituted poly‐p‐phenylene (PPP) and the Raman spectra of Na‐doped PPP excited at 488.0 and 1064 nm were observed and compared with the corresponding spectra for the ordinary (12C) polymer. 13C substitution is shown to be useful for characterizing not only the bands of intact PPP but also those of polarons and bipolarons generated in Na‐doped PPP. The number of Raman bands observed for bioplarons (and also for polarons) is greater than that for intact PPP. This observation is explained as the result of the loss of translational symmetry in the regions of these local excitations.
Double‐resonant Raman scattering by LO‐phonons in quantum wells in a magnetic field
Authors: Govorov A. O.
Published: May 2005

One‐LO‐phonon resonant Raman scattering in quantum wells in the presence of the magneto‐polaron effect was investigated theoretically. The cross‐section of Raman scattering involving uncorrelated electron–hole pairs as intermediate states was calculated using the parabolic model of valence bands. An analysis showed that the magneto‐polaron effect plays an important role in double‐resonant Raman processes. The Raman intensity under double‐resonant conditions in a magnetic field is strongly increased by α−1 times, where α is the electron–phonon coupling constant. The Fröhlich and deformation‐potential electron–phonon interactions are considered for different scattering configurations in a model of confined phonons.
Raman scattering study of (NH4)3−xRbxZnBr5 single crystal
Authors: Krylov A. S. , Schäfer A. D. , Vtyurin A. N.
Published: May 2005

The lattice dynamics of a recently synthesized crystal of (NH4)3−xRbxZnBr5 were studied by Raman spectroscopy. The spectra were found to be in good agreement with the crystal structure. Clear evidence of NH4 group disorder was found. Ordering of these groups at low temperatures was observed.
Micro‐Raman study of ion‐irradiated oxidized silicon surfaces
Authors: Tripathi R. , Kar S. , Bist H. D.
Published: May 2005

Micro‐Raman studies were performed on ion‐irradiated oxidized silicon surfaces with different ion energies, ion fluences and subsequent hydrogenation to determine the efficacy and sensitivity for obtaining information on the degree of ion beam‐induced damage in very thin (ca. 100 Å) layers of silicon subsurface and the top oxide. The variations in the Raman spectra were interpreted in terms of the degree of amorphization produced in the silicon sub‐surface by the ion beam and depolymerization of the top SiO2 layer.
Broad background bands in Raman spectra of alumina studied by both visible and near‐infrared excitation
Authors: Mortensen A. , Christensen D. H. , Nielsen O. Faurskov , Pedersen E.
Published: May 2005

Raman spectra were obtained for two different samples of alumina. One is usually used as a support for hydro‐treating catalysts in heterogeneous catalysis and the other was synthesized in the laboratory. Different excitation wavelengths were used: 457.9, 488.0, 514.5, 647.1 and 1064 nm. The commercially available alumina showed an intense broad background with excitation in the near‐infrared region, whereas no significant background was observed with visible excitation. The synthetic alumina showed a broad background band with laser excitation in the visible region. It is shown that the appearance of these backgrounds is not due to fluorescent impurities (e.g. iron, chromium or organic compounds). Tentative explanations of the spectral features are provided in terms of density of states (alumina A) or bulk hydroxyl groups (alumina B).
Infrared reflectance and Raman spectra of lithium triborate single crystal
Authors: Xiong Guisheng , Lan Guoxiang , Wang Huafu , Huang Chaoen
Published: May 2005

Infrared reflectance and Raman spectra of LBO crystals were recorded at room temperature and liquid nitrogen temperature. The vibrational modes are classified by the factor group analysis method and the spectral bands are assigned to vibrations of the (B3O6)3− ring and BO4 tetrahedra.
Enhancement factor of surface‐enhanced Raman scattering on silver and gold surfaces upon near‐infrared excitation. Indication of an unusual strong contribution of the chemical effect
Authors: Hildebrandt Peter , Keller Stefan , Hoffmann Andreas , Vanhecke Franck , Schrader Bernhard
Published: May 2005

Surface‐enhanced Raman (SER) spectra of the xanthine dyes rhodamine 6G (R6G) and oxazine 1 (OX1) were measured with near‐infrared excitation employing Fourier transform Raman spectroscopy. Both dyes exhibit strong SER signals on Ag and Au surfaces. The enhancement factors were evaluated based on the determination of the number of adsorbed molecules. In the absence of additional electrolyte, the enhancement factors for R6G on Ag and Au sols are 1.3 × 104 and 1.6 × 104, respectively. This enhancement is operative for all adsorption sites and is ascribed to the classical electromagnetic mechanism. On activation of the Ag sol by chloride ions, the enhancement factors for R6G and OX1 are 4.3 × 107 and 7.6 × 105, respectively. This increased enhancement which occurs at a small number of specific adsorption sites is ascribed to the charge‐transfer mechanism. For R6G this enhancement mechanism is stronger by a factor of 47 than for visible excitation. The electrolyte‐induced activation is not possible for Au sols or precipitates of Ag or Au on filter‐papers. These metal‐coated filter‐papers may provide appropriate SER‐active surfaces for analytical applications of the SER effect in combination with Fourier transform Raman spectoscopy.
Raman scattering study of phase transitions in undoped and rare earth ion‐doped BaCeO3 and SrCeO3
Authors: Scherban T. , Villeneuve R. , Abello L. , Lucazeau G.
Published: May 2005

Polycrystalline samples of perovskite‐structured BaCeO3 and SrCeO3 were studied by Raman scattering spectroscopy in the temperature range 77–983 K. Changes in the spectra of BaCeO3 with temperature are explained in terms of a second‐order phase transition (D2h → D4h) at T0 = 427 K. Analysis of the temperature dependence of soft modes suggests a partial displacive character. A dramatic decrease in band intensity above 1000 K indicates a transition to the cubic (Oh) structure, for which no Raman bands are expected. The Raman spectra of SrCeO3 indicate that no phase transitions occur in the temperature range 77–983 K. Room temperature spectra of BaCeO3 doped with various rare earth ions (Nd3+, Gd3+, Yb3+) are compared. Doping with 5 and 10 mol.% Nd stabilizes the high‐temperature tetragonal and cubic phases, respectively. The crystal structure is a sensitive function of Nd dopant concentration.
Photodissociation of (DMSO)2Fe(II)PPIX to form a transient five‐coordinate complex as studied using transient resonance Raman spectroscopy
Authors: Nalliah R. E. , Findsen E. W.
Published: May 2005

Resonance Raman spectra of iron(II) protoprophyrin IX [Fe(II)PP] in dimethyl sulfoxide (DMSO) and deuterated DMSO were obtained at high and low photon densities using 10 ns laser pulses. At low photon density, comparison of the Raman spectra of the complex with those of carbonmonoxy‐hemoglobin indicates that a low‐spin, six‐coordinate (DMSO)2Fe(II)PP complex exists; at high photon density, spectral comparisons with deoxyhemoglobin and the 2‐methylimidazole heme complex (2‐MeIm)Fe(II)PP indicate that a transient high‐spin, five‐coordinate complex is formed by photodissociation of a DMSO ligand. This phenomenon is reversible and observable on a 10 ns time‐scale.
Raman spectra of piperazine hexahydrate and N–D stretches by polarons
Authors: Kanesaka Isao , Kuwano Kazuhiko , Ishioka Tsutomu
Published: May 2005

The Raman spectrum of deuterated piperazine hexahydrate shows a new band that is red shifted from the main ND stretch by 38 cm−1. The intensity of this band increases at low temperatures. It is proposed that this band arises from polarons. Although the corresponding new band is not resolved in the NH stretch region of the hydrogenated system, the band width increases on cooling, which suggests the appearance of a new band due to polarons. The less resolved spectral feature in the hydrogenated system is discussed.
Nafion‐supported metal complexes: a resonance Raman and UV–visible spectroscopic study
Authors: Maclean Angela L. , Armstrong Robert S. , Kennedy Brendan J.
Published: May 2005

Resonance Raman and UV–visible spectra of cobalt tetraphenylporphyrin and cobalt phthalocyanine in Nafion were recorded. The spectroscopic measurements show that the porphyrin is incorporated into the hydrophobic regions of the polymer whilst the phthalocyanine is associated with the ionic domains. The macrocycles undergo a change in geometry in Nafion, the porphyrins exhibiting a decreased core size in the membrane.
Automated interpretation of Fourier transform Raman spectra of complex polymers using an expert system
Authors: Claybourn M. , Luinge H. J. , Chalmers J. M.
Published: May 2005

The feasibility of applying an expert system for the interpretation of Raman spectra of complex acrylic and styrenated acrylic copolymers was demonstrated. The rules for the interpretation were generated automatically within the expert system from peak tables of the relevant homopolymer spectra. Application of these rules to copolymers gave excellent interpretation results without giving false negatives or false positives. Although the sensitivity limit for detection was not determined for the structural fragments characterized, components in copolymers were identified with very high probabilities down to theca. 15% (w/w) level, indicating that the lower limit is much less than this.
Relative SERS enhancement factors for pyridine adsorbed on a silver electrode. The chemical effect in SERS as a product of charge‐transfer and active‐site mechanisms
Authors: Kudelski A. , Bukowska J. , Jackowska K.
Published: May 2005

The relative SERS (surface‐enhanced Raman scattering) enhancement factors for pyridine adsorbed on a silver electrode were determined as a function of the laser wavelength and applied potential. The charge‐transfer (CT) effect on Raman intensity, GCT, was determined by analysing the relative Raman intensity as a function of the potential, taking into account voltage‐dependent coverage of the silver electrode. The total chemical effect was defined as a product of GCT and the so‐called ‘active‐sites’ effect and was estimated as equal to about 50.
Raman and far‐infrared spectra of formamide at temperatures down to 20 K
Authors: Torrie B. H. , Brown B. A.
Published: May 2005

The Raman and infrared wavenumbers of solid HCONH2 and DCOND2 were measured at 20 K and high temperatures. More peaks were observed in both the lattice and internal mode regions than were expected from the known structure, so the structure was redetermined. The resulting structure is in agreement with earlier determinations, so the extra peaks are attributed to second‐order effects produced by a large anharmonicity associated with the hydrogen bonds. Attempts to model the structural details and the lattice dynamics had only a limited success, which may again be attributed to anharmonic effects and to the basic inadequacies of the models.
Surface‐enhanced Raman spectra using silver‐coated paper substrates
Authors: Lee Arthur S. L. , Li Ying‐Sing
Published: May 2005

Because of the importance of developing an active substrate for surface‐enhanced Raman (SER) spectroscopic applications, a silver‐coated filter‐paper substrate was prepared for surface‐enhanced Raman scattering (SRS) by using a chemical reduction method at room temperature. Optimization of the silver deposition time was achieved by using p‐nitrophenol (PNP) as an analyte. Its performance as an SERS‐active substrate was tested using PNP, p‐chlorobenzoic acid, m‐chlorobenzoic acid and o‐chlorobenzoic acid. To overcome the problem of low enhancement when a dipping method was adopted for sample applications, a silver‐coated alumina‐based substrate was prepared. The new substrate was found to exhibit strong SERS with both the solution and the dipping methods for sample applications of PNP. Using the new substrate, the limit of detection for methyl red was estimated to be 3 ng ml−1.
Micro‐Raman study of BaTiO3 thin films prepared by the metallo‐organic decomposition technique
Authors: Ching‐Prado E. , Katiyar R. S. , Santiago‐Aviles J. J.
Published: May 2005

A micro‐Raman probe was used to characterize thin films of barium titanate synthesized by metallo‐organic decomposition and rapid thermal annealing techniques. All films were found to be polycrystalline aggregates with perovskite as the primary phase. The optimum film processing procedure as evidenced by the micro‐Raman probe was a combination of rapid thermal annealing at 950°C in an oxygen or argon atmosphere. Fourier transform infrared spectra indicated that samples annealed in a vacuum show higher carbon contamination than those receiving the same heat treatment in an oxygen or argon atmosphere.
Construction of third and fourth rank tensors for the triclinic, monoclinic and orthorhombic crystal classes
Authors: Leuchs M. , Kiefer W.
Published: May 2005

A simple method is described for constructing symmetry‐allowed polar tensors for n‐photon processes of rank three and four by using polar tensors of rank one and two. The consideration is restricted here to the triclinic, monoclinic and orthorhombic crystal classes and intrinsic symmetry is not taken into account. Expansion to higher order tensors is possible.
Solid‐phase transitions in TlHSO4 crystal
Authors: Le Calve N. , Pasquier B. , Romain F. , Taffin A.
Published: May 2005

Polycrystalline TlHSO4 was investigated by calorimetry (253–423 K) and by infrared (10–300 K) and Raman (10–420 K) spectroscopy. Two phase transitions are detected at 320 and 388 K. A complete assignment of the spectra of the room‐temperature phase (III) is given and the spectroscopic results are consistent with infinite chains of hydrogen bonds. This structure appears disordered above 320 K (phase II). The high‐temperature phase (I) presents the characteristic features of a plastic phase according to the spectroscopic manifestations of an increasing orientational disorder of sulphate ions. Above 360 K, a metastable phase (I′) showing a complex hydrogen‐bonded framework is identified.
Instrument for natural and magnetic Raman optical activity studies in right‐angle scattering
Authors: Hecht Lutz , Barron Laurence D.
Published: May 2005

A simple computer‐controlled instrument for natural and magnetic incident circular polarization Raman optical activity (ICP ROA) measurements in right‐angle scattering is described. The key spectral elements consist of a fast single‐stage monochromator equipped with a holographic notch filter, a highly efficient holographic diffraction grating and a thinned back‐illuminated, thermoelectrically cooled charge‐coupled device (CCD) detector. A temperature‐stabilized longitudinal electro‐optic modulator is employed to switch between orthogonal circular polarization states in the incident laser radiation. A polaroid film together with a mica half‐wave retardation plate are used to select particular linear polarization states in the Raman scattered radiation with the same instrumental response. High‐quality depolarized and polarized Stokes and depolarized anti‐Stokes ICP ROA spectra of (R)‐(−) and (S)‐(+)‐phenyloxirane and depolarized magnetic resonance ICP ROA spectra of copper(II) tetrabromide are presented as typical examples of the excellent performane characteristics.
Resonance CARS studies on acridine in the electronic excited T1 state
Authors: Bischof T. , Kiefer W.
Published: May 2005

CARS measurements were carried out on acridine to investigate the resonance behaviour of the totally symmetric vibration in the lowest excited triplet electronic state. The lineshapes of the observed vibrational mode were analysed for different pump laser wavenumbers by means of the transform theory in the Condon approximation. Under this condition the experimentally determined CARS excitation profile was compared with that calculated from the measured Tn ←T1, absorption spectrum.
Vibrational spectra and conformations of isopropyl thiocyanate and its d6 and d7 deuterated analogues
Authors: Jozwiak R. N. , Karlsson A. , Klaeboe P. , Nielsen C. J.
Published: May 2005

The Raman and IR spectra of isopropyl thiocyanate, isopropyl‐1,1,1,3,3,3,‐d6 thiocyanate and isopropyl‐d7 thiocyanate were recorded as vapours, liquids and amorphous and crystalline solids. IR matrix isolation spectra were recorded in argon and in nitrogen matrices at 14 K, using the hot nozzle technique. Two conformers with Cs, symmetry (anti) and C1, (gauche) were present in the vapour and liquid states whereas only one conformer (anti) existed in the crystal. The enthalpy difference was measured to be ΔH° (gauche‐anti) = 2.4 ± 0.2 kJ mol−1 in the liquid from variable‐temperature Raman spectra. In argon matrices a value of 2.3 ± 0.3 kJ mol−1 was obtained in the temperature range 300–600 K, similar to the value in nitrogen matrices, both assumed to be valid for the vapour phase. Annealing experiments indicated the barrier of gauche–anti conversion to be around 9 kJ mol−1. Quantum chemical calculations with the basis sets STO–3G, 3–21G* and 6–31G* were carried out The energy difference between the conformers was calculated and scaled ab initio force constants were employed in normal coordinate calculations. Complete assignments of Raman and IR bands belonging to the anti conformer of the parent molecule and the isotopomers were carried out. Only a limited number of bands characteristic of the gauch conformer were observed since most of its Raman and IR bands overlapped those of the anti conformer.
Assignment of adenine ring in‐plane vibrations in adenosine on the basis of 15N and 13C isotopic frequency shifts and TUV resonance Raman enhancement
Authors: Toyama Akira , Hanada Naoki , Abe Yoshiharu , Takeuchi Hideo , Harada Issei
Published: May 2005

Infrared, Raman and UV resonance Raman spectra of adenosine and its 1,3‐15N2, 2–13C, and 8–13C isotopic analogues were measured in neutral aqueous solution (Raman and UV Raman) and in the crystalline state (infrared and Raman). The observed isotopic wavenumber shifts are useful in distinguishing adenine ring vibrations from ribose vibrations. In‐plane modes of the adenine ring are selectively enhanced in UV resonance Raman spectra, which facilitates the assignment of the in‐plane vibrations. In addition to the in‐plane modes, a ribose vibration coupled with adenine in‐plane vibrations was identified in the UV resonance Raman spectra. The fundamental wavenumbers for 22 in‐plane normal modes of the 9‐substituted adenine ring of adenosine in the 1700–250 cm−1 region are proposed. Although the fundamental wavenumbers of adenosine correspond well with those of adenine above 1350 cm−l and below 800 cm−1 the vibrations in the 1350–800 cm−1, region are appreciably affected by the presence of the N‐9—C‐1′ glycosidic bond and the couplings between ribose and adenine ring vibrational motions. The adenosine fundamental wavenumbers and their isotopic shifts reported here may be useful in analysing vibrational spectra of adenine nucleosides and nucleotides and in improving the force field of the 9‐substituted adenine ring.
Application of near‐infrared‐Fourier transform Raman spectroscopy in medical research
Authors: Keller Stefan , Schrader Bernhard , Hoffmann Andreas , Schrader Wolfgang , Metz Klaus , Rehlaender Achim , Pahnke Jörg , Ruwe Markus , Budach Wilfried
Published: May 2005

Using NIR–FT Raman spectroscopy we have obtained useful spectra of many kinds of biomaterials. These spectra contain—with only simple sample preparation—information that can be used both for component analysis and for tissue identification. In addition, pathological changes in the spectra of eye lenses and of brain, liver and colon tissues are observed, demonstrating the usefulness of the technique as a tool of medical diagnosis.
Vibrational conformational analysis of ethyl formate
Authors: Maes I. I. , Herrebout W. A. , van der Veken B. J.
Published: May 2005

Infrared (4000–50 cm−1) spectra of gaseous, amorphous and crystalline ethyl formate, HCOOCH2CH3, were recorded. Raman spectra of the gaseous, liquid and solid phases were investigated from 3500 to 25 cm−1. Additionally, qualitative depolarization ratios were obtained from the Raman spectra of the liquids. Ab initio calculations were carried out using a 4–21G basis set and show that the compound can occur as four possible conformers, s‐cis trans, s‐cis, gauche, s‐trans trans and s‐trans, gauche. Their optimized structural parameters, their force field and the vibrational wavenumbers and potential energy distributions were calculated for each conformer. Additionally, the potential function governing internal rotation from the s‐trans, trans to the s‐cis trans conformation was calculated. Both the s‐cis conformers were identified in the vibrational spectra of the gaseous, amorphous and fluid phases, and there are strong indications that a weak band at 623.5 cm−1 in the Raman spectrum of the fluid phases is due to one of the s‐trans conformers. From a temperature study of the Raman spectrum of the liquid, the enthalpy difference between the cis, trans and s‐cis gauche conformers was determined to be 1.4 ± 0.4 kJ mol−1 with the trans conformer being the more stable rotamer. Vibrational spectra of the crystalline solid, which consists only of the s‐cis, trans conformer, showed that ethyl formate can crystallize in two different forms. A complete assignment of the vibrational fundamentals from the infrared and Raman spectra is proposed.
Confocal three‐dimensional scanning laser Raman–SERS–fluorescence microprobe. Spectral imaging and high‐resolution applications
Authors: Sharonov Sergey , Nabiev Igor , Chourpa Igor , Feofanov Alexey , Valisa Paolo , Manfait Michel
Published: May 2005

A multi‐purpose instrument which allows the recording of confocal micro‐Raman, micro‐SERS and micro‐fluorescence spectral images of sample areas from 5 × 5 to l50 × l50 μm with a lateral resolution of ca. 0 3 μm and an axial resolution of ca. 1 μm was developed. The instrument is a combination of two spectrometers both coupled to the same microscope, motorized sample stage, confocal entrance chamber, macro‐sample chamber and CCD detector. The first spectrometer includes a double monochromator coupled with a spectrograph and exhibits the properties of a typical high‐resolution Raman instrument permitting measurements of the low‐wavenumber regions of the spectra. The second spectrometer includes a Notch filter and a spectrograph equipped with two interchangeable low‐dispersion gratings and exhibits the properties of a high‐luminosity spectrometer, suitable for low resolution, over a wide spectral range and highly sensitive micro‐Raman and microfluorescence measurements. The choice of spectrometer most suitable for a particular application can be made automatically without additional prealignment of the system. The system of optical scanners operating in the confocal mode and two‐dimensional CCD detection allow the accumulation of spectra from hundreds of points of the sample under the microscope simultaneously. A computer‐controlled scanning sample stage and a system using a ‘scanning line’ of the laser beam allow fast recording of well resolved confocal spectral images (CSI) without sample degradation. Conventional images of species could be recorded with a TV–CCD camera through the microscope optics. The software supports all stages of CSI recording and allows the combined treatment of conventional and spectral images including their spatial calibration and conversion of spectral image into a conventional image, to assign point‐by‐point the spectral data to the conventional image. The applicability of the instrumentation and techniques to the study of polymeric materials, industrial samples and fluid inclusions in minerals was demonstrated. Spectral images based on the micro‐SERS analysis of an antitumour drug adsorbed on the hydrosol were recorded and are discussed in terms of their application to the micro‐SERS imaging studies of living cells.
Crossing of anisotropic and isotropic Raman components in the intermolecular resonance coupling of vibrations. II—LiClO4 and LiI solutions in acetone
Authors: Kecki Zbigniew , Sokolowska Anna
Published: May 2005

Changes in the wavenumbers of the anisotropic and isotropic components of the CO stretching band in the Raman spectrum of LiClO4 and Lil solutions in acetone were investigated. The non‐coincidence values defined as Δν = νaniso – viso of the CO band in LiCIO4 solutions were positive for bulk acetone and negative for the acetone‐shared ion pairs. In LiI solutions, where the separation of bulk acetone was not possible, the non‐coincidence values changed from positive to negative with increasing concentration of LiI. A mechanism for the non‐coincidence changes is proposed.
Raman and infrared spectra, conformational stability, barriers to internal rotation, vibrational assignment and ab initio calculations of 3‐bromo‐2‐methylpropene
Authors: Durig J. R. , Eltayeb Saadia , Guirgis Gamil A.
Published: May 2005

The Raman (3200–20 cm−1) and infrared (3200–35 cm−1) spectra of 3‐bromo‐2‐methylpropene, H2CC(CH3)CH2Br were recorded for the gas and solid. Additionally, the Raman spectrum of the liquid was recorded and qualitative depolarization values were obtained. The fundamental asymmetric torsional mode for the gauche conformer is observed at 81.5 cm−1 with one excited state falling at a lower wavenumber but the asymmetric torsion is not observed for the higher energy s‐cis conformer. Utilizing the gauche observed torsional wave numbers, the gauche dihedral angle, the enthalpy difference between conformers and the calculated torsional fundamental wavenumber for the s‐cis conformer, the potential function governing the interconversion of the rotamers was estimated. This potential function gives values of 170 cm−1 (486 cal mol−1) (1 cal = 4.184 J), 2659 cm−1 (7.60 kcal mol−1) and 725 cm−1 (2.07 kcal mol−1) for the s‐cis to gauche, gauche to gauche and gauche to s‐cis barriers, respectively, and it is compared with tht obtained with the RHF/STO‐3G* basis set. From the methyl torsional wavenumber of 172 cm−1 for the gauche conformer, the threefold barrier of 695 cm−1 (1.99 kcal mol−1) was calculated for the methyl group. A complete vibrational assignment is proposed based on Raman : depolarization data, group wavenumbers and relative infrared and Raman intensities. The conformational energy difference and optimized geometries of both conformers were also obtained from ab initio calculations with the RHF/STO‐3G*, RHF/LANL1DZ and MP2/LANL1DZ basis sets. Normal‐coordinate analyses were also performed with force fields determined from both the RHF/STO‐3G* and RHF/LANL1DZ basis sets. The calculated wavenumbers support the proposed vibrational assignment. These data are compared with the corresponding data for some similar molecules.