bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spectroscopy at very high pressures: 45—structural phase transitions in A2HgI4, (A = Ag, Cu, Tl, 1/2Pb), investigated by Raman scattering
Authors: Adams David M. , Hatton Peter D. 
Published: May 2005

AbstractRaman spectra and phonon pressure dependencies are reported for the spinel‐related iodides A2HgI4, (A = Ag, Cu, Tl and 1/2Pb) at high pressures in a diamond anvil cell. In each case the upper pressure limit of observation was set by changes in band gap which caused darkening and photodecomposition. New phase transitions were found for Cu2HgI4 (8 and 25 kbar), Tl2HgI4 (11.5 kbar) and PbHgI4 (7 and 14 kbar). Transitions in Ag2HgI4 were located at 3.3, 5.9 and 8.1 kbar, confirming and extending earlier evidence. The β‐Ag2HgI4 to phase II transition at 3.3 kbar appears to be second‐order in type. Using Landau's theory, Ag2HgI4 II was shown to adopt space group C. Similarly, at the I/II transition in Cu2HgI4, the new phase (II) can have either D or C symmetry.
A Raman spectroscopic study of the structural phase transition and reorientational motions of the ClO ions in KClO4
Authors: Toupry N. , Poulet H. , Le Postollec M. , Pick R. M. , Yvinec M. 
Published: May 2005

AbstractPolarized Raman spectra of oriented single crystals of KClO4 performed over a large temperature range (300–800 K) have been used to investigate the mechanism of the 583 K phase transition. It is shown that the transition can be described using an order parameter and a mechanism based on the reorientation of the ClO ions is proposed. A Raman study of the plastic phase (above 583 K), using the shape of the bands associated with the internal modes, leads to a measure of the orientational density probability and the orientational self‐correlation functions of the perchlorate ions.
Analyse Vibrationnelle des Acides Cyclobutanedicarboxyliques‐1,3 cis et trans en Solution Aqueuse: 2—L'Acide Cyclobutanedicarboxylique‐1,3 trans et le Cyclobutanedicarboxylate Dipotassique
Authors: Fabrègue Eliane , Cassanas Geneviève , Bardet Lucette , Escale Roger , Chapat Jean‐Pierre 
Published: May 2005

AbstractUne étude par RMN a montré que l'acide cyclobutanedicarboxylique‐1,3 trans a en solution aqueuse une conformation gauche axiale‐équatoriale. L'analyse des spectres de polarisation Raman prouve que ee composé n'a aucune symétrie, tandis que le dianion cyclobutanedicarboxylate appartient au groupe de symétric Cs, les plans des deux groupements carboxylates étant orthogonaux. Une attribution des fréquences des vibrations fondamentales est proposée pour chaque composé.
Raman spectra of alkali halide/NCO− systems
Authors: Mohammad M. R. , Sherman W. F. 
Published: May 2005

AbstractThe Raman spectra of twelve different alkali halide/NCO− systems have been investigated, and these spectra have been compared with the previously‐studied infrared spectra. In the external mode region there are significant differences in the infrared and Raman spectra associated with the in‐band features.
Raman and infrared spectra of calcium and barium sulphamates
Authors: Muthusubramanian P. , Sundara Raj A. 
Published: May 2005

AbstractRaman spectra of a single crystal of calcium sulphamate and polycrystalline barium sulphamate have been recorded at room temperature. Infrared spectra of polycrystalline calcium and barium sulphamates for the region 20‐4000 cm−1 are also presented. The assignments made are supported by potential energy distribution calculations. The data show that there is no water of hydration in barium sulphamate. The N‐S torsional mode is observed in both the compounds. This has not been found in other sulphamates of this family. The results indicate very weak hydrogen bonding in these crystals.
The polarized Raman spectra of CsCdCl3 single crystals
Authors: Kuok M. H. 
Published: May 2005

AbstractRaman scattering measurements on CsCdCl3 single crystals have been made at 15 K. First‐ and second‐order phonon scattering are observed and the symmetry species of the first‐order spectrum have been partly determined by means of polarization studies.
Raman spectral studies of bleomycin A2 and related structural fragments: A probe for bleomycin–DNA interactions
Authors: Freedman Teresa B. , Santillo Frank S. , Zimba Carl G. , Nafie Laurence A. , Dabrowiak James C. 
Published: May 2005

AbstractRaman spectra have been obtained for bleomycin A2 and selected fragments. Virtually all of the features in the bleomycin Raman spectrum can be attributed to the preresonance enhanced vibrational transitions of the 2,4′‐bithiazole moiety as determined by comparison to the Raman spectra of bithiazole fragments. The Raman spectrum of bleomycin is dominated by a very intense band at 1542 cm−1 that can be approximately assigned as a bithiazole ring stretching mode. This feature may serve as a probe of bithiazole environment in bleomysin ‐DNA interactions.
Hyper‐Raman spectra and frequency dependence of soft mode damping in SrTiO3
Authors: Denisov V. N. , Mavrin B. N. , Podobedov V. B. , Scott J. F. 
Published: May 2005

AbstractThe hyper‐Raman spectra of SrTiO3 were studied in the range 85–710 K. The temperature dependance of frequencies and damping of all the vibrations, including the soft F1u and silent F2u modes, was obtained. Using the hyper‐Raman spectra and a Green's function analysis, we calculated the damping function Γs(ω, T) in the frequency region 20–200 cm−1 for temperatures between 300 and 710 K. It was shown that the behavior of the soft mode damping may be described by invoking soft mode decay into two acoustic phonons (ωs→ωac+ωac) plus an additional channel via annihilation of one acoustic phonon (ωs+ωac→ω176). The temperature dependence of the phonon resonance between the soft mode and the nearest polar optical phonon (at 176 cm−1) was studied. Quantitative analysis of this phonon resonance was carried out to obtain parameters characterizing both modes: signs and relative magnitude of the hyper‐Raman matrix elements; the soft mode damping; and the resonance coupling constant, which yields interference effects.
Carbonyl stretching vibrations of uracil studied by 18O isotopic substitutions with UV resonance Raman spectroscopy
Authors: Chinsky L. , Hubert‐Habart M. , Laigle A. , Turpin P. Y. 
Published: May 2005

AbstractResonance Raman spectra of uracil and its 18O isotopically substituted species (in positions 2‐, 4‐ and 2,4‐) have been obtained in neutral aqueous solutions with 257 nm excitation. A computer decomposition of the 1560‐1740 cm−1 region showed the presence of five bands in this region, at 1629, 1659, 1673, 1689 and 1706 cm−1 in the case of uracil. The shifts and intensity variations caused by isotopic substitution are also reported, and these help precise assignments of these bands. The discussion also takes into account the resonance Raman spectra of 2‐ and 4‐thiouracil and 2,4‐dithiouracil, obtained with 300 nm excitation.
Influence of Faraday rotation on the selection rule of phonon Raman scattering in magnetic materials
Authors: Peng‐Xiang Zhang , An Tu 
Published: May 2005

AbstractWe report the first examination of the influence of Faraday rotation on the selection rule of phonon Raman scattering in magnetic materials. It is shown that the original selection rule for phonons will no longer be valid owing to the introduction of Faraday rotation. By applying a transverse ( is the direction of light propagation) or a longitudinal () magnetic field, the effect of Faraday rotation can be switched off or on. The changes of the intensity and mode structure of phonon scattering in the two configurations are related directly to the absorption and the magneto‐optical figure of merit, Q ( = θF/2α, where θF is the specific Faraday rotation and α is the coefficient of absorption). The result also shows that introducing Faraday rotation offers a new chance of identifying some vibration modes which are otherwise impossible. Taking garnet (O) as example, the relationship between phonon scattering intensities and Faraday rotation and absorption was calculated for typical scattering configurations. The results can be checked experimentally using magnetic materials with suitable Q values.
Surface‐enhanced Raman spectra of aromatic amino acids and proteins adsorbed by silver hydrosols
Authors: Nabiev Igor R. , Savchenko Vladimir A. , Efremov Evgeniy S. 
Published: May 2005

AbstractSurface‐enhanced Raman spectra of some amino acids (Phe, Tyr, Trp, His, Leu and Ala) and cytotoxin I from Naja naja oxiana adsorbed by silver hydrosols have been obtained. The spectra are enhanced from 100 to 200 times. Addition of aqueous solutions of the amino acids to the hydrosol resulted in the appearance of an absorption band in the visible spectral range (450–650 nm) due to formation of the hydrosol‐amino acid complex. The surface‐enhanced Raman spectrum and the absorption band disappear after short ultrasonic treatment of the complex. Comparison of electron microphotographs of the silver hydrosol and the hydrosolprotein complex clearly demonstrate coagulation of the silver micelles, apparently caused by protein adsorption and complex formation. The excitation profile of the Phe‐Ag hydrosol complex was obtained and this agreed well with the position of the longwave absorption band. From the analysis of the intensity ratios of the Stokes and anti‐Stokes components of the Raman spectra of Phe in the silver hydrosol and in aqueous solution the mechanism of the resonance Raman effect is strongly supported. The problem of possible conformational changes of the adsorbed molecules was considered. From CD spectra of cytotoxin I in aqueous solution and those in the silver hydrosol it was concluded that the backbone conformation of the protein did not change, but the environment of the aromatic residues altered. Experiments on the binding of an equimolar mixture of Phe and Ala with silver hydrosols showed that competitive binding took place, and thus the aromatic amino acid is mainly responsible for the surface‐enhanced Raman effect.
Resonance Raman spectra of iron(II) and ruthenium(II) complexes with perdeuteriated 2,2′‐bipyridine
Authors: Strekas Thomas C. , Mandal Santosh K. 
Published: May 2005

AbstractResonance enhanced Raman spectra are reported for the complexes M(bpy‐d8)32+[MFe(II), Ru(II)] and Ru(bpy‐d8)2Cl2, where bpy‐d8 is perdeuteriated 2,2′‐bipyridine. Correlations are made with the corresponding resonance enhanced modes of the hydrogen containing compounds for the spectra obtained in resonance with the visible metal to ligand charge‐transfer (MLCT) absorption bands. In particular, the effect of in‐plane CH(D) deformation modes on the resonance active vibrations is discussed.
Unit cell group analysis of orthorhombic crystals: Detailed investigation of the effect of arbitrary choice of axes
Authors: Rulmont A. 
Published: May 2005

AbstractThe results of the group theoretical analysis of the normal vibrations of crystals having orthorhombic space groups can depend on the arbitrary choice of axes because there is no unambiguous way to define a unique axis. This situation creates some confusion in the results published by different authors. We have investigated in detail the problem of the unit cell group analysis of the orthorhombic structures D2h and D2 and the results are presented in two tables for practical applications. It is shown that it is possible to express the irreducible representations as a function of experimental parameters, which gives a clearer view of the physical situation than the conventional notation (Ag etc.).
Vibrational spectra of tribromoacetonitrile and [15N] tribromoacetonitrile
Authors: Arenas J. F. , Marcos J. I. , Suero M. I. 
Published: May 2005

AbstractThe IR and the low‐frequency Raman spectra of liquid tribromoacetonitrile and its 15N isotopic derivative were recorded and assigned on the basis of isotopic shifts and depolarization ratios. The isotopic product rule has been successfully applied by assuming a CNDO optimized geometry.
The resonance Raman spectrum of silver permanganate
Authors: Jubert A. H. , Varetti E. L. , Baran E. J. 
Published: May 2005

AbstractThe resonance Raman spectrum of a polycrystalline sample of AgMnO4 allowed a wider insight into the vibrational properties of the MnO ion in this lattice. This study confirmed important covalent contributions to the overall structure and strong cooperative effects between the ions present in the unit cell.
Vibrational spectra of specifically deuteriated 2,2′‐bipyridine complexes of Fe(II), Ru(II) and Os(II)
Authors: McClanahan Stephen , Kincaid James 
Published: May 2005

AbstractThe resonance Raman spectra of specifically deuteriated divalent d6 metal complexes are reported. These include the iron(II) and ruthenium(II) perdeuteriated complexes and the Ru(bpy‐3,3′‐d2)32+ and Ru(bpy‐6,6′‐d2)32+ complex ions. The syntheses of the deuteriated ligands are reported and the frequency shifts observed on deuteriation are correlated with the natural abundance iron(II), ruthenium(II) and osmium(II) complexes.
Vibrational spectra and conformational behavior of (cyanomethyl)cyclopropane
Authors: Wurrey C. J. , Yeh Y. Y. , Weakley M. D. , Kalasinsky V. F. 
Published: May 2005

AbstractThe infrared spectra (4000–400 cm−1) of gaseous, liquid and solid (cyanomethyl) cyclopropane have been recorded for the first time. Additionally, the Raman spectra (3500–50 cm−1) of condensed phases of this substance have also been obtained. ‘Extra’ Q branches have been observed in the gas‐phase infrared spectrum, and six liquid‐phase Raman doublets (two of which are also seen in the infrared spectrum of the liquid) have also been observed, wherein one member of each doublet vanishes once the polycrystalline solid state spectrum is obtained. These data have been interpreted in terms of a two conformer (gauche/cis) fluid‐phase equilibrium for (cyanomethyl)cyclopropane, with only the gauche conformer remaining in the solid phase. The temperature behavior of the 774/756 and 835/855 cm−1 liquid‐phase Raman doublets yields an enthalpy difference between conformers of 0.72±0.10 kcal mol−1, with the gauche conformer the more stable. This ΔH value implies a room‐temperature conformational equilibrium for (cyanomethyl)cyclopropane composed of 87% gauche and 13% cis rotamers in the liquid phase. In addition, a vibrational assignment for the 33 normal modes of (cyanomethyl)cyclopropane has been proposed, and it is in excellent agreement with the previously published vibrational assignments for three (halomethyl)cyclopropanes.
Hydrogen bonding in hydrogen peroxide and water. A Raman study of the liquid state
Authors: Giguère Paul A. , Chen Hung 
Published: May 2005

AbstractThe Raman spectra of pure, anhydrous H2O2 and its deuteriated analogues, D2O2 and HDO2, were examined in the liquid state up to 40 °C and supercooled down to −75 °C. The OH (OD) stretching bands show a broad, single‐peaked contour, and a strongly temperature‐dependent asymmetry‐ Decomposition by analog computer reveals two overlapping bands, about 100 cm−1 apart, with different temperature behavior. In contrast with water, there is no indication in the hydrogen peroxide spectra of ‘free,’ i.e. non‐hydrogen‐bonded, OH groups, in keeping with the flexible geometry of the molecule and its electronic configuration. Based on these spectra, and by analogy with water, a two‐state model is proposed featuring a continuum of hydrogen‐bonded H2O2 molecules, with elose‐packed OH groups in two kinds of environments. The hydrogen bonds are slightly weaker (12–15%) than those in water. Hydrogen peroxide is the best analog for studying the structure of water.
Raman spectra of the III → II phase transition in normal (d0) and deuteriated (d12) tetramethylammonium chlorides
Authors: Pal Mahendra , Agarwal Anshu , Patel M. B. , Bist H. D. 
Published: May 2005

AbstractA design of a high‐temperature cell (used with a Spex‐1403 Ramalog spectrophotometer) for Raman studies with 90° geometry is given. Raman spectra of normal (d0) and denteriated (d12) tetramethylammonium chlorides in phases III and II are reported, together with their assignments. On the basis of the temperature dependence of the thermosensitive bands, the III → II phase transition was found at 367 ± 2 K for normal (d0) tetramethylam monium chloride and at 407±5 K for deuteriated (d12) tetramethylammonium chloride. It is observed that the III → II phase transition is irreversible if the samples are kept under vacuum during the investigation. Traces of moisture present in the samples are responsible for the stability of the room‐temperature phase III.
Vibrational spectra of 4, 4′‐difluorobiphenyl‐d8 and the structure of biphenyls in solution
Authors: Pulham R. J. , Steele D. 
Published: May 2005

Abstract4, 4′‐Difluorobiphenyl‐d8 was synthesized by two routes and its infrared and Raman spectra were recorded. These were analysed with the assistance of calculated frequencies using a force field based on fluorobenzenes and using phase effects. A perturbation treatment of the frequencies of biphenyl, of its 4, 4′‐difluoro derivative and of their fully deuteriated isotopomers yielded a refined force field essentially in accord with previous aromatic fields. By studying the changes in the frequencies of certain skeletal modes on going from crystal to solution, the dihedral angle of the difluoro compound was shown to be very similar to that of biphenyl itself in solution (35–40°). There is, however, a possibility that the present model underestimates the in‐plane B1g skeletal deformation mode. In this case the biphenyl dihedral angle will be slightly overestimated and that of 4, 4′‐difluorobiphenyl slightly underestimated (by up to 5°).
Raman, infrared, fluorine NMR spectra and rotational isomerism of perfluoromethyl oxalate
Authors: Cutín E. H. , Védova C. O. Della , Varetti E. L. , Aymonino P. J. 
Published: May 2005

AbstractThe Raman spectra of solid and liquid perfluoromethyl oxalate and its IR spectra in the gaseous, solution (CCl4) and solid phases have been recorded. The fluorine NMR spectrum of the substance in CCl4 solution has also been obtained. A comparison of the vibrational spectra in the solid and fluid phases shows that perfluoromethyl oxalate exists in the fluid phases as a conformational mixture, whereas in the solid phase it seems to exist as a single conformer of trans‐planar C24 structure. A band assignment has been attempted for the normal vibrational modes of this conformer.
Raman spectroscopic detection of a low‐temperature structural phase transition in distearoyl phosphatidylcholine bilayers
Authors: Madec C. , Wong P. T. T. , Mantsch H. H. 
Published: May 2005

AbstractA new structural phase change at − 6 °C was found in aqueous dispersions of distearoyl phosphatidylcholine. The thermotropic gel‐gel phase transition at −6 °C exhibits first‐order characteristics and is equivalent to the barotropic phase transition on chain length is discussed.
Raman spectra and normal coordinate analysis of the planar vibrations of iron phthalocyanine
Authors: Melendres C. A. , Maroni V. A. 
Published: May 2005

AbstractRaman spectra have been obtained for solid iron phthalocyanine and a 10−6 M solution of its tetrasulfonated derivative with Kr+ laser excitation using the 6471 Å line. A normal coordinate analysis was carried out to determine assignments for the observed frequencies in terms of the various Raman active planar modes of vibration of the complex. Good agreement was obtained between calculated and observed frequencies using an adjusted valence force field (AVFF) and incorporating empirical correlations for related types of force constants. The assignments of the normal modes of vibration appear to be generally consistent with other avilable experimental and theoretical information for phthalocyanine complexes and the related metalloporphins; however, the extensive mixing of the internal coordinates within the calculated normal modes shows clearly that the assignment of specific vibrational frequencies to individual internal coordinates is not justified. Rather, the vibrational kinematics appear to involve concerted motions of the various interior and exterior ring systems.
Theory of depolarization ratios in diatomic molecules for continuum resonance Raman scattering and application to 79Br2
Authors: Baierl P. , Kiefer W. 
Published: May 2005

AbstractA theory is presented for the calculation of depolarization ratios of the Q‐branches of diatomic molecules for the case of resonance with continuous (dissociative and/or repulsive) excited electronic states. The theory was applied to the 79Br2 molecule and calculations of the depolarization ratios of the fundamental Q‐branch and accompanying hot bands were performed for different excitation frequencies. Comparison with experimentally obtained depolarization ratios showed good agreement.
Degree of circular polarization of resonance Raman scattering–luminescence discrimination and assignment of non‐totally symmetric modes in [Ph4P][ReS4]
Authors: Peacock Robert D. , Stewart Brian 
Published: May 2005

AbstractThe degree of circular polarization, C(π), has been measured for resonance Raman scattering from the [ReS4]− ion in a microcrystalline sample at 10 K. There is considerable partially relaxed luminescence which is discriminated against by this technique. The relative values of C(π), observed for components of resonantly enhanced Raman bands, provide evidence for assignments to non‐totally symmetric modes of the ion.
Raman intensities and electro‐optical parameters of the azide ion in β‐NaN3 single crystals and aqueous solution
Authors: Bertsch Gerhard , Rösinger Gerold , Eysel Hans H. 
Published: May 2005

AbstractRaman spectra of oriented β‐NaN3 single crystals were taken in b(cc)a, b(cb)a, a(bb)c and a(ba)c orientations. Because of the simple structure R3m (Z = 1), the observed intensities can be interpreted on the basis of an oriented gas model. A new assignment is given for the weak bands: 1278 cm−1 (Eg of 2ν2), 1269 cm−1 (A1g of 2ν2), 1260 cm−1 (A1g of 030←010), 1368 cm−1 (110←010). Electro‐optical parameters and first‐order bond moments are calculated for the NN bonds: a∥=3.47 Å2, α′⊥=1.33 Å2, μ=0.57 D, dμ/dr=8.34 D Å−1.
Analyse Vibrationnelle et Structurale en Série Aliphatique Saturée VI–Spectres de Vibration de l'acide Diéthylmalonique et de ses sels Alcalins en Solution Aqueuse
Authors: Delarbre J. L. , Maury Bardet L. Et L. 
Published: May 2005

AbstractLes spectres Raman et infrarouge de l'acide diéthylmalonique et de ses sels alcalins en solution aqueuse (H2O et D2O) ontété étudiés dans le domaine 3500‐200 cmminus;1. L'analyse du facteur de dépolarisation des raies Raman nous permet de conclure que l'acide diéthylmalonique et le sel neutre, comme I'acide diméthylmalonique et son sel neutre, appartiennent au groupe de symétrie C2 tandis que le sel acide répond au groupe Cs; I'existence d'une liaison hydrogéne intramoléculaire dans le sel acide est discutée. Une attribution des vibrations fondamentales est proposée.
Hyper‐Raman spectra and polariton‐vibration resonances in liquid C2Cl4 and PCl3
Authors: Denisov V. N. , Mavrin B. N. , Podobedov V. B. , Sterin Kh. E. 
Published: May 2005

AbstractThe polarized hyper‐Raman spectra and the polaritons were studied in liquid PCl3 and C2Cl4. The TO‐LO splitting of the dipole modes was found in PCl3 [480 (TO)‐515 (LO) cm−1 and 494 (LO)‐500 (TO) cm−1]. The LO and TO mechanical modes vanished in the back‐scattering and forward‐scattering hyper‐Raman spectra, respectively. The possibility of observation of the splitting due to polariton‐vibration resonance is analysed. It is shown that the observation at ω≲300 cm−1 is possible if the oscillator strength of the vibration exceeds 0.1. Using the value of the splitting, the oscillator strengths were estimated for a number of dipole modes in PCl3 and C2Cl4. The trend of the polariton branches and the observation of the resonances showed that all dipole modes of a liquid have the same symmetry, although the symmetry of these modes was different when considered in terms of the 'molecular' selection rules. To analyse the selection rules of the vibrational spectra of liquids it is necessary to invoke its macroscopic symmetry.