bluuebunny/crossref_metadata_2025_split huggingface dataset:
Raman spectroscopic studies on sodium metavanadate
Authors: Seetharaman S. , Bhat H. L. , Narayanan P. S. 
Published: May 2005

AbstractSodium metavanadate (NaVO3) has been reported earlier to exhibit ferroelectric behaviour below 380 °C, but unlike many other known ferroelectrics it does not show a very strong dielectric anomaly, indicating that the structural change during the ferroelectric phase transition may be only a slight modification of the paraelectric phase. This is in conformity with the x‐ray data at room temperature, which could be refined to the same R value either in space group C2/c or Cc. Further, it is known that NaVO3 occurs also in another polymorphic modification (β‐form), the structure of which has not been established. Raman spectroscopic studies of single crystals of the α‐form of NaVO3 have been carried out and a crystalline powder of the β‐form has been made. The Raman spectra have been interpreted in terms of the linear VO chains formed by VO4 tetrahedra sharing two corners with each other. The temperature variation of the intensity and width of the Raman lines through the phase transition has been measured and the observed LOTO splitting in the room temperature phase confirm the Ce ferroelectric space group.
Chromium oxide film thickness measurements using spontaneous Raman scattering
Authors: England W. A. , Jenny S. N. , Greenhalgh D. A. 
Published: May 2005

AbstractQuantitative measurements of chromium oxide film thicknesses on pure chromium have been made using Raman scattering. The results are compared with those from argon ion erosion. Possible developments of the technique to the chemical mapping of corrosion film using Raman scuttering are discussed.
Infrared and Raman spectra and crystal structure of solid bromotrifluoromethane
Authors: Park Y. S. , Shnrvell H. F. 
Published: May 2005

AbstractInfrared and Raman spectra of polycrystalline films of CF3 Br have been recorded at 77 K. All six fundamentals of the molecule have been observed in both spectra. Observed splittings of fundamentals have been attributed to Fermi resonance (ν1), bramine isotope splitting (ν3) and crystal splitting (ν4, ν5 and ν6). Some bands due to 13CF3 Br have also been identified. The crystal splittings can be explained if it is assumed that the structure is monuclinic with factor group C2h and two molecules per unit cell on sites of Cs symmetry.
Vibrational analysis and normal coordinate calculations of the o‐phthalic acid molecule
Authors: Colombo L. , Volovšek V. , Lepostollec M. 
Published: May 2005

AbstractRaman and infrared vibrational spectra have been recorded for o‐phthalic acid as a single crystal, as a powder and in solution. The proposed assignment of the observed frequencies was made on the basis of a normal coordinate analysis and symmetry considerations of the crystal spectrum, which allowed the separation of internal vibrations of the A and B species.
The vibrational spectrum of the ammonia‐hydrogen cyanide system and the normal coordinate analysis of NX4CN (X=H or D)
Authors: Kanesaka Isao , Kawahara Hisakazu , Kiyokawa Yoshinobu , Tsukamoto Masaki , Kawai Kiyoyasu 
Published: May 2005

AbstractThe vibrational spectrum of NX4CN (X=H or D) at 77 K is reported. The splittings of the internal modes of the NX ion are slight and the internal modes and the librations correspond well in frequency with those in related compounds. The observed bands are assigned on the basis of normal coordinate analysis to the crystal structure of D and C symmetries, where there are slight differences in the calculated frequencies by use of the same force constants. In 2NX3·XCN ν4 of the NX ion splits, resulting in an associated species of [X3NX…︁NX3]+. Associated species and the site of the CN− ion are discussed with CN stretchings observed in 2NX3·XCN and NX3·2XCN.
Single crystal Raman studies on magnesium sulphite trihydrate, MgSO3·3H2O and MgSO3·3(H, D)2O
Authors: Lutz H. D. , Henning J. , Buchmeier W. , Engelen B. 
Published: May 2005

AbstractThe Raman and infrared spectra of MgSO3·3H2O and of deuteriated and isotopically dilute samples of this hydrate were recorded from 100 to 4000 cm−1 at 90–300 K and analysed with regard to the bonding structure of the water of crystallization, the space group of this compound, i.e. P212121, Pnma or Pn21a, and assignment and coupling (with the H2O and D2O librations) of the internal modes of the sulphite ions. The orientational behaviour of single crystal Raman studies on isotopically dilute samples are firstly used for assigning the uncoupled OH (OD) stretching modes to the H positions in the lattice. From the three types of water of crystallization (in the case of space group P212121 or Pn21a), the orientationally disordered H2O1 and H2O11 are involved in very strong hydrogen bonds, uncoupled OH (OD) modes 3027 (2282) and 2930 (2240) cm−1, caused by the strong hydrogen bond acceptor strength of the sulphite ions. Both water molecules are extremely distorted with OH (OD) mode splittings up to 393 (218) cm−1, the largest known so far. H2O111 forms weak bifurcated hydrogen bonds. Both the stretching and bending vibrations of the sulphite ions coincide with rotational modes of the water molecules.
Bifurcated hydrogen bonds in water
Authors: Giguère Paul A. 
Published: May 2005

AbstractA new model is proposed for liquid water, based on recent studies of the Raman spectra as a function of temperature. It features two kinds of hydrogen bonds: in addition to the well known linear hydrogen bonds (LHB), predominant in cold water, there are some bifurcated hydrogen bonds (BHB) between three water molecules. These three‐centered bonds, mainly electrostatic, have an average energy of 2.5 kcal mol−1, about half of that of the LHB. Their characteristic OH stretching frequency is around 3420–3440 cm−1, compared with 3220 cm−1 for the LHB. In addition, there are a few percent of nearly free OH groups, i.e. non‐hydrogen‐bonded (NHB), with a stretching frequeney of ca 3615 cm−1. Reorientation between these three states occurs through rotation of the H2O molecules about one of their OH bonds. Thus, on melting, one third of the hydrogen atoms move out of the tetrahedral framework to occupy interstitial sites in the open ‘shafts’ characteristic of the ice structure. As in the case of ice, Fermi resonance between the ν1 and 2ν2 levels has little impact on the vibrational spectra of liquid water and iee. The hybrid molecule, HDO, does not form LHB with H2O or D2O, hence its simpler spectra. The BHB model can account much better than previous models for the thermodynamic anomalies of water.
Laser microzone damage in surface‐enhanced Raman scattering by pyridine on cooper electrodes
Authors: Mernagh Terrence P. , Cooney Ralph P. 
Published: May 2005

AbstractSurface‐enhanced Raman scattering (SERS) by pyridine on anodized copper electrode surfaces has been shown to arise from laser damage zones. On the basis of pH dependence studies, the intensely scattering species appears to be a copper complex. Evidence for semi‐macroscopie laser damage zones (ca 0.1 mm in diameter, ca 500 nm or ca 1400 atom layers in depth) emerges from laser perforation of thin film electrodes, visual examination, scanning electron micrescopy (SEM), Raman line intensification for laser illumination during the oxidation‐reduction cycle (ORC), uniform laser‐flux perturbations of the cyclic voltammograms and laser interruption intensity studies. These results argue for a much reduced metal surface enhancement factor for this system and against the use of copper SERS effects in studies of electrosorption on undamaged surfaces. SERS from this system at excitation wavelengths greater than 620 nm is expected to involve conventional (non‐surface)resonance enhancement arising from copper(II)‐pyridine complexes (λmax ⩾ 590 nm) formed by copper corrosion within the laser damage zone. On the basis of these findings the Cu/pyridine system has been classified as SERS Type III.
Raman intensities of propane in the gas phase
Authors: Martin J. 
Published: May 2005

AbstractAn experimental and theoretical study of the vibrational Raman intensities of propane in the gas phase is presented. The absolute scattering coefficients and depolarization ratios corresponding to clearly separated spectral zones (made up of one or more vibrational modes) have been measured. The absolute scattering coefficients and depolarization ratios for each normal vibrational mode have been determined theoretically using the hypothesis that bond polarizabilities are transferable. Ethane parameters from previous work and the vibrational eigenvectors deduced from a propane force field given in the literature were used to apply this hypothesis.
Tuning metal island films for maximum surface‐enhanced Raman scattering
Authors: Aroca Ricardo , Martin Fernando 
Published: May 2005

AbstractEnhancement factor calculations based on the electromagnetic model of surface‐enhanced Raman scattering (SERS) are presented for a series of metals. The specific dependence of SERS on the excitation and vibrational frequencies, and the aspectratio of spheroidal particles, are discussed. It is suggested that the results are relevant for experiments carried out on metal‐island surfaces.
Vibrational spectra of chlorocyclopropane
Authors: Green P. M. , Wurrey C. J. , Kalasinsky V. F. 
Published: May 2005

AbstractThe gas‐phase Fourier transform infrared spectrum (4000‐400 cm−1) of chlorocyclopropane was recorded at a resolution of 0.5 cm−1. For the first time, gas‐phase Raman and solid‐phase infrared and Raman spectra were obtained for this molecule. Liquid‐phase Raman and infrared spectra were also recorded and, on the basis of all the data, a complete assignment of the 21 normal modes of vibration of chlorocyclopropane was made. The proposed assignment is in excellent agreement with assignments for other substituted cyclopropanes and, in particular, other chlorine‐substituted cyclopropanes.
Raman and far infrared spectra of crystalline acetylene, C2H2 and C2D2
Authors: Anderson A. , Andrews B. , Torrie B. H. 
Published: May 2005

AbstractRaman and far infrared spectra of the orthorhombic and cubic phases of acetylene and deuterated acetylene have been obtained. In the orthorhombic phase, three of the four expected librations have been identified in the Raman spectrum and the two infrared active translations have been confirmed, for both samples. In the cubic phase, two of the three predicted librations in the Raman spectrum and the expected pair of translations in the far infrared spectrum have been observed, again for both samples. Splittings in the internal mode Raman spectra are, with one exception, in agreement with the predictions of group theory.
Rotational Raman optical activity in chiral symmetric tops
Authors: Barron L. D. , Johnston C. J. 
Published: May 2005

AbstractA theory of rotational Raman optical activity in chiral symmetric top molecules is presented. The required rotational transition polarizability and optical activity tensors are calculated using irreducible tensor methods for axially symmetric systems. Selection rules on optically active rotational Raman scattering are found to be basically the same as for conventional rotational Raman scattering, namely ΔJ = 0, ±1, ±2 with ΔK = 0, but in addition to possessing an anisotropic polarizability, the molecule must be chiral and must possess an anisotropy in the electronic optical activity tensors. A measure of this optical activity anisotropy is provided by the dimensionless circular intensity difference in a resolved rotational Raman band or in the envelope of unresolved bands provided the envelope is resolved from the central sharp Rayleigh line. A group polarizability model is used to calculate the rotational Raman optical activity in a chiral (D3) conformation of triphenylborane.
Normal‐coordinate analysis of 5‐methyl‐2‐thiocytosine and its oxygen analogue and assignments of the Raman and infrared bands
Authors: Aruna S. , Shanmugam G. 
Published: May 2005

AbstractThe infrared and Raman spectra of 5‐methyl‐2‐thiocytosine and its oxygen analogue in the solid state were recorded in the range 4000–200 cm−1. Normal coordinate calculations were performed for these compounds using a simple Urey‐Bradley force field for the in‐plane vibrations and a valence force field for the out‐of‐plane vibrations of the planar skeleton. The assignments of the vibrational fundamentals were made on the basis of normal coordinate calculations and the frequency shifts of bands on N‐deuteriation, The assignments are discussed in relation to vibrational assignments of some related molecules.
Resonance Raman spectra of poly(L‐lysine), aromatic amino acids, L‐histidine and native and thermally unfolded ribonuclease A
Authors: Chinsky L. , Jolles B. , Laigle A. , Turpin P. Y. 
Published: May 2005

AbstractUsing excitation radiation of wavelength 248 nm, the peptide linkages of poly(L‐lysine) give rise to important pre‐resonance enhancements in the Raman spectra of the amide bands, specially of the amide II band located in the 1550–1570 cm−1 shift region. Using the same excitation wavelength, aromatic amino acids and histidine exhibit resonance enhancement, and their resonance Raman spectra are easily obtainable without a fluorescence background contribution. This background is very large, particularly in the case of phenylalanine when longer wavelength excitation is used. The Raman spectra of native and thermally denatured ribonuclease A have been investigated using 248 nm excitation radiation. These spectra show the major contribution of the tyrosine residues of the protein. It seems that the behaviour of the tyrosine doublet is not a completely adequate probe for following the unfolding of the protein.
Temperature dependence of the Raman spectrum of the plastic solid carborane p‐C2B8H10: Investigation of the phase transitions, orientational disorder and the behaviour of the so‐called ‘background’
Authors: Bukalov S. S. , Leites L. A. 
Published: May 2005

AbstractThe temperature dependence of the Raman spectrum of the plastic solid carborane p‐C2B8H10 was studied in the range 15–470 K. Unlike the icosahedral carboranes C2B10H12, this ‘stretched’ carborane has only one plastic phase, probably with anisotropic reorientations. A phase transition to an ordered crystal takes place at 188 K. In a sealed capillary the substance melts at 433 K. The Raman spectrum of p‐C2B8H10, originally having no background, acquired the background after the sample had been repeatedly heated and cooled. It was found that the background intensity depends on the thermal prehistory of the sample; it slowly diminishes on heating, and several degrees below the melting point the background disappears completely and re‐emerges in the spectrum of the melt.
Resolution enhancement in spectroscopy by maximum entropy fourier self‐deconvolution, with applications to Raman spectra of peptides and proteins
Authors: Ni Feng , Scheraga Harold A. 
Published: May 2005

AbstractThe method of maximum entropy extrapolation is applied to Fourier self‐deconvolution to enhance the inherently low resolution of the Raman spectra of peptides and proteins. Using computer‐simulated and real spectral data, a comparative study was made between the maximum entropy (MEM) and the conventional discrete Fourier transform (DFT) methods. The MEM provides better resolution with no side‐lobe formation, and is especially useful in the resolution enhancement of complicated Raman spectra of proteins. The MEM is also suitable for the spectral estimation of a short‐time record of noisy data, enabling the exposure time of protein solutions to the intense laser beam to be reduced significantly. The theory of maximum entropy spectral analysis is presented and the application of the techniques of digital resolution enhancement is discussed. It is pointed out that a combined use of different techniques should be made whenever possible in carrying out digital signal enhancement in order to reduce the chance of misinterpretation of spectral information.
Raman microspectroscopy of LiDNA fibres in ethanol and tert‐butanol
Authors: Mud J. , Otto C. , De Mul F. F. M. , Greve J. 
Published: May 2005

AbstractThe conformation of low‐salt LiDNA in fibrous form has been studied by Raman microspectroscopy. The recorded spectrum of a fibre soaked in ethanol is very similar to that of a fibre at low relative humidity. From x‐ray experiments it is known that in the latter case the DNA adopts the C conformation. Therefore, it can be concluded that this is also the case in a low‐salt LiDNA fibre soaked in ethanol. Further, it has been observed that the DNA conformation did not change when the excess ethanol was allowed to evaporate. The C form is also found when the fibre is in contact with ethanol vapour only. These results are in agreement with x‐ray studies. However, our experiments with a LiDNA fibre in tert‐butanol are not in agreement with x‐ray results. Only when the tert‐butanol is absolutely free from water is a state intermediate between the B and C forms found.
Isotropic Raman band shape and vibrational relaxation for molecules in the liquid state: A Critical study of some band shape functions
Authors: Fujita Kazuyoshi , Fukuda Takuya , Fukushi Kohji , Kimura Masao 
Published: May 2005

AbstractA band shape function for the isotropic Raman scattering described in terms of the band width in the weak coupling limit and the relaxation time of the bath mode has been proposed by summing the results of Berne et al. [J. Chem. Phys. 45, 1086 (1966)], Wang [Mol. Phys. 33, 207 (1977)] and Knauss [Mol. Phys. 36, 413 (1978)]. The results of band analyses with this function have been compared with those obtained from other conventionally used band shape and correlation functions. The present function is preferable for precise interpretation of vibrational relaxation mechanisms, particularly for those cases where temperature and concentration dependence of the band parameters are involved.
Pure rotational and vibration–rotational Raman spectra of 1H2, 1H2H and 2H2
Authors: Edwards H. G. M. , Farwell D. W. , Gorvin A. C. , Long D. A. 
Published: May 2005

AbstractThe pure rotational (S‐branch) and vibration‐rotational (Q‐branch) Raman spectra of 1H2, 1H2H and 2H2 have been recorded photographically and analysed with a precision greater than that achieved in earlier investigations to produce values of the bond lengths. From a combination of these results and those obtained from the species 2H3H, 1H3H and 3H2 a mean value of the bond length in the equilibrium configuration of re = 74.151±0.001 pm has been obtained.
CARS spectrometer with cw intra‐cavity excitation for high‐resolution Raman spectroscopy
Authors: Frunder H. , Matziol L. , Finsterhölzl H. , Beckmann A. , Schrötter H. W. 
Published: May 2005

AbstractThe construction of a cw CARS spectrometer is described, consisting of a single mode argon ion ring laser, an intra‐cavity sample cell and a tunable dye laser. The argon laser was first stabilized to an iodine absorption line. From an evaluation of the CARS spectrum of the Q‐branch of the rovibrational band of nitrogen, the vibration‐rotation interaction constant is obtained as αe = 0.0173850 ± 0.0000035 cm−1, in agreement with Bensten's result from the linear Raman spectrum of the total band. Finally, the stabilization of the argon laser to a hyperfine component in the Doppler‐free polarization spectrum of iodine is described.
Effect of electrolyte concentration on the Raman spectra of water in aqueous solutions
Authors: Rull F. , de Saja J. A. 
Published: May 2005

AbstractPolarized Raman spectra of water in the ν(OH) and δ(OH2) regions have been recorded for aqueous solutions of electrolytes of types AB and AB2 (A = Li, Na, K, Ca; B = Cl, Br, I, NO3) over a wide concentration range. Variations in frequencies, intensities, band shapes and band widths with changes in concentration and in the nature of the ions are discussed.The isotropic and anisotropic components of the intensity of the ν(OH) band have been analysed as a function of concentration. It is found that the function 45(a')2 is approximately independent of, or decreases slightly with, the concentration of the alkali metal halides whereas for the nitrates it increases linearly with concentration. The function 3(γ′)2 increases very slowly with concentration for both halides and nitrates. These results have been compared with those obtained for pure water when the temperature is varied over the range −20 to 120°C.Despite the difference in nature of the two types of perturbation (ionic and thermal), all the results can be interpreted in terms of modifications of intra‐and inter‐molecular couplings and Fermi resonance between vibrational modes of water molecules.
Effect of hydrostatic pressure on the phase state and molecular structure of aqueous lysolecithins: A Raman spectroscopic study
Authors: Wong Patrick T. T. , Mantsch Henry H. 
Published: May 2005

AbstractThe Raman spectrum of aqueous palmitoyl lysolecithin was monitored as a function of pressure between 1 bar and 26.1 kbar. The changes observed in these Raman spectra are discussed in terms of the effect of hydrostatic pressure on the phase state and the molecular structure of lysolecithins. At pressures between 1 and 1900 bar aqueous palmitoyl lysolecithin exists in a micellar state and at pressures above 1.9 kbar it converts into a series of three coagel phases. The critical pressures at 28°C are 1.9 kbar for the micellar to coagel I transition, 4 kbar for the coagel I to coagel II transition and 15 kbar for the coagel II to coagel III transition. The transition from the micellar phase to the coagel I phase has a high pressure hysteresis of 1.1 kbar, while the transitions between the three coagel phases show only negligible pressure hysteresis. The major change in structure occurs at 1.9 kbar where the cylindrical micellar phase converts to an interdigitated lamellar coagel phase; the structural changes at 4 kbar (coagel I/II transition) and at 15 kbar (coagel II/III transition) involve only a modification of the interchain packing.
Effect of vinyl groups on resonance Raman spectra of protoporphyrin‐IX
Authors: Sarkar M. , Verma A. L. 
Published: May 2005

AbstractResonance Raman (RR) spectra obtained with several excitation wavelengths are compared for the following porphyrin‐IX compounds: free‐base protoporphyrin‐IX, meso‐porphyrin‐IX and haematoporphyrin‐IX and copper‐protoporphyrin‐IX and copper‐mesoporphyrin‐IX dimethyl esters. Certain bands in the RR spectra of all the free‐base porphyrins or copper complexes are unaffected with respect to frequency, whereas there is a shift in the frequencies of some vibrational modes in some systems. From a comparative study of the systems which have identical geometrical arrangements, no extra features were found in the RR spectra of protoporphyrin which can be attributed directly to the vinyl group modes. This suggests that the vibrational modes of vinyl groups do not distort the excited electronic state substantially, and are not effective in vibronic coupling with the electronic states of the porphyrin macrocycle and therefore do not gain intensity under resonance excitation. Most of the vibrational modes are strongly coupled and there are no extra distinct features in the RR spectra of PP which may be associated with selective vibrational coupling of the vinyl group modes with the porphyrin skeletal modes.