bluuebunny/crossref_metadata_2025 huggingface dataset:
Spectra and structure of small ring compounds. Part LVI—Raman and far‐infrared spectra, conformational stability vibrational assignments, normal coordinate analysis and ab initio calculations of chlorocyclobutane
Authors: Durig J. R. , Lee Min Joo , Little T. S.
Published: May 2005

The Raman (3100 to 10 cm−1) and far‐infrared (374 to 74 cm−1) spectra have been recorded of gaseous chlorocyclobutane. A series of Q‐branches observed in both of these spectra beginning at 158 cm−1 with successive transition falling to lower frequencies have been assigned to the ring puckering vibrations of both the low‐energy equatorial and high‐energy axial conformers. These data have been fitted to an asymmetric potential function of the form V (cm−1) = (5.13 ± 0.34) × 105X4 − (3.35 ± 0.14) × 104X2 + (3.79 ± 0.30) × 104X3 with a reduced mass of 198 amu. Utilizing this potential, the difference between the puckering angles for the two conformers was calculated to be 5° with the equatorial conformer having the larger value of 22°. This potential function is consistent with an energy difference between the equatorial and axial forms of 449 cm−1 (1.28 kcal mol−1) and a barrier to ring inversion of 827 cm−1 (2.36 kcal mol−1). Experimental values for the enthalpy difference between the two conformers have been determined for both the liquid and gas from relative intensities of a pair of Raman lines. The conformational stability, barrier to ring inversion, ro structural parameters, and fundamental vibrational frequencies, which have been determined experimentally, are compared with those obtained from ab initio Hartree‐Fock calculations employing both the 3–21G* basis sets, and to the corresponding quantities obtained for some similar molecules. The ab initio results indicate that the puckering angle for the equatorial conformers should be about 30°, with that for the axial conformer being about 8° smaller.
Concentration‐dependent depolarized Raman spectra of HCl and DCl in solution in liquid carbon dioxide
Authors: Stidham Howard D. , Ewen Mark E.
Published: May 2005

The depolarized component of Paman scattering by pure liquid HCl and DCl and of solutions of these acid halides in liquid CO2 are reported. At room temperature the band contours show no S branch intensity in pure acid halide liquid, but in solution in liquid CO2 and S branch is increasingly evident with increasing CO2 concentration. The frequency shifts are a function of the dielectric constant and refractive index of the solution. Reorientational correlation functions calculated from the anisotropic scattering decay more slowly in the first few tens of femtoseconds than predicted for monomeric acid halides, suggesting contribution to the composite correlation function by species of larger moments of inertia but vibrational frequencies identical with those of the monomers.
Electronic parameter determination for potassium chromate by coherent anti‐stokes Raman spectroscopy
Authors: Bostick J. M. , Carreira L. A. , Antcliff R. R.
Published: May 2005

Two separate methods of spectral analysis have been used to analyze the CARS spectra of K2CrO4 at pump wavelengths near its electronic transition. The Jacobian least‐squares line‐fitting method requires initial guesses for parameters and returns directly the best iteratively fitted parameters. These were then used to plot the relative magnitudes of the Lorentzian and dispersive components, i.e. imaginary and real terms, respectively, of these bands. The FREIGHT–CARS method of spectral phase extraction was used to yield directly the relative values of the Lorentzian and dispersive components. A comparison of the values obtained by both methods shows a fundamental agreement between the relative magnitudes of these parameters. In both analyses, the Lorentzian contribution to the resonance region is seen to approach a maximum near the electronic absorption.
Dispersion of depolarization ratio and reversal coefficient in vibrational resonance Raman scattering by polyatomic molecules
Authors: Morozov V. A.
Published: May 2005

Analytical expressions for the depolarization ratio and reversal coefficient in vibrational polyatomic Raman scattering are derived using the wave packet formulation. Some changes in the dispersion of the depolarization ratio and reversal coefficient caused by changes in the vibronic coupling and by various shifts of nuclear equilibrium positions on molecular electronic excitation which have not been reported before have been studied.
High‐frequency vibrational mode characterization of Zn(II), Ni(II) and Co(II) tetraphenylchlorins
Authors: Song Ok‐Keun , Ha Jong‐Seo , Yoon Minjoong , Kim Dongho
Published: May 2005

The detailed resonance Raman spectra of metallotetraphenylchlorins with B, Qx and Qy excitations and excitation profiles of Raman modes on the Qy absorption band have been reported. In metallotetraphenylchlorins, the character of the vibrational eigenvector and the localization of the modes in the pyrrole rings raised by the symmetry are different from those of metallooctaethychlorins. A recent normal mode calculation on Cu(II) tetraphenlchlorin based on the semi‐empirical quantam chemistry force field (QCFF/PI) method was utilized to elucidate the vibrational mode assignment of Zn(II), Ni(II) and Co(II) tetraphenylchlorins. For Raman excitation profiles on Qy(O, O) and Qy(O, 1) absorption bands, it is observed that some polarized Raman bands have contributions not only from A‐term scattering but from Herzberg‐Teller scattering. This can be explained by the symmetry lowering and the localized normal mode character of metallotetraphenylchlorins. For depolarized and anomalously polarized Raman bands, the vibronic coupling (interstate mixing) is strongly introduced.
Surface‐induced substitution reaction on cobalt(III) and manganese(III) tetrakis (4‐N‐methylpyridyl)porphyrins probed by surface‐enhanced Raman spectroscopy
Authors: Ha Jong‐Seo , Song Ok‐Keun , Yoon Minjoong , Kim Dongho
Published: May 2005

The Surface‐enhanced Raman spectra of Co(III)TMPyP(4)Cl and Mn(III)TMPyP(4)Cl [where TMPyP(4) = tetrakis (4‐N‐methylpyridyl)porphyrin] demonstrate the formation of Ag(II)TMPyP(4) on the silver surface. The reaction is not photon assisted but is dependent on the sol activity and time. The effect of NaCl on the sol activity and the surface‐induced reaction was investigated. It was observed that the metal substitution reaction of Mn(III)TMPyP(4)Cl was more efficient than that of Co(III)TMPyP(4)Cl.
Determination of molybdenum–oxygen bond distances and bond orders by Raman spectroscopy
Authors: Hardcastle Franklin D. , Wachs Israel E.
Published: May 2005

A correlation is developed for relating Raman stretching frequencies of molybdenum–oxygen (MoO) bonds to their respective bond distances in molybdenum oxide compounds. MoO bond orders are also related to stretching frequencies. The MoO correlation is expected to offer invaluable insight into the structures of molybdate species in chemical systems which are not amenable to analysis by diffraction or other spectroscopic techniques. In the present study, the correlation is used to predict stretching frequencies for perfect MoO4 and MoO6 structures, and to determine MoO bond distances of the MoO6 octahedron in Ba2CaMoO6 as well as the dehydrated surface molybdate species in MoO3/Al2O3.
The MCGA (multiple cubic gradient approximation) method for the analysis of Raman spectra
Authors: de Mul F. F. M. , ten Have H. B. G. , Otto C. , Greve J.
Published: May 2005

An easily accessible interactive method for the analysis of Raman spectra consisting of many overlapping peaks is presented. A combination of a three‐ or four‐dimensional grid and gradient searching is applied. The method can handle spectra with up to about 50 lines, based on a broad background. Analytical and user‐defined or tabulated basic functions can be included. The merits of the method are discussed with both artificial and real spectra.
Preresonance Raman spectra of methylpyridines
Authors: Kosmidis C. , Bolovinos A. , Tsekeris P.
Published: May 2005

Preresonance Raman spectra of methylpyridines (picolines) are presented for different incident laser wavelengths. A strong intensity variation of the non‐totally symmetric vibration 10α is observed, which implies a vibronic coupling of the lowest nπ* excited state with the next ππ* (B2u and B1u) states. In addition an intensity increase of some totally symmetric vibrations is observed and their possible implications for the geometry of the excited ππ* states are discussed.
IR and polarized Raman spectra of KIO3 · Te(OH)6
Authors: Santha N. , Nayar V. U.
Published: May 2005

The IR and polarized Raman spectra of the addition compound KIO3 · Te(OH)6 were recorded and analysed. Bands indicate that the IO3− ion is distorted in this crystal and its symmetry is less than its free ion symmetry, C3ν. The TeO6 ion occupies a lower symmetry, C1, than its free ion symmetry, Oh.
High‐resolution non‐linear Raman spectroscopy in gases
Authors: Schrötter H. W. , Berger H. , Boquillon J. P. , Lavorel B. , Millot G.
Published: May 2005

The resolution in the Raman spectra of gases has been greatly improved by the development of the different methods of non‐linear Raman scattering. When two laser beams, one of which has a tunable frequency, are focused in a sample, a stimulated Raman process occurs as soon as the frequency difference between the two lasers is equal to a Raman‐active rovibrational or rotational transition frequency. The Raman resonance can be detected in different ways: by coherent anti‐Stokes Raman scattering (CARS) or the corresponding Stokes process (CSRS), by a gain in one of the beams (stimulated Raman gain spectroscopy, SRGS) or a loss in the other (inverse Raman spectroscopy, IRS), or even by detection of a photoacoustic signal (photoacoustic Raman spectroscopy, PARS). The selective ionization of the excited molecules by a third ultraviolet laser (ionization‐detected stimulated Raman scattering, IDSRS) has considerably increased the sensitivity in special cases.

The instrumental resolution is determined by the convoluted line widths of the lasers used for excitation. The narrowest line widths can be achieved with stabilized continuous‐wave lasers. Their relatively low power has been compensated for either by intracavity excitation of CARS spectra or by injection locking of dye laser amplifiers which are pumped by pulsed lasers or by flashlamps. Examples of investigations of the structure of rovibrational bands and of line‐width measurements as a function of pressure are reviewed.
Measurments of collisional line widths in the stimulated Raman Q‐branch of the ν1 band of silane
Authors: Millot G. , Boutahar A. , Lavorel B. , Wenger C. , Saint‐Loup R. , Berger H.
Published: May 2005

Self‐broadened widths of 28SiH4 in the ν1 Q‐branch have been measured at room temperature (295 K) using high‐resolution stimulated Raman Spectroscopy. These collisional widths have been obtained by fitting a super‐position of Voigt profiles to the experimental spectra in the pressure range 28–154 Torr. No evidence for line mixing within the tetrahedral components of a Q(J) line has been found. The line broadening coefficients for J up to 13 depend weakly on the rotational quantum number. The mean value is 103.7 × 10−3 cm−1 atm−1.
Raman spectroscopy of coexisting phases in TbP5O14
Authors: Chen Ting , Scott J. F.
Published: May 2005

At temperatures above the monoclinic‐orthorhombic P21/c‐Pcmn phase transition at 180°C in terbium pentaphosphate, the presence of a third phase was observed spectroscopically, identified as a C2/c monoclinic structure. Two lines at 12 and 17 cm−1 were observed to grow in intensity as the temperature was raised from 180 to 240°C; they would be described as acoustic modes at the Brillouin zone boundary in the Pcmn phase, made Raman‐active by the doubling of the unit cell along the c‐axis in the C2/c phase. The interpretation of these lines resolves a question concerning the asymmetry (‘shoulder’) of the soft optic mode at the P21/c‐Pcmn ferroelastic transition raised long ago.
Etude en Microspectrometrie Raman de l'Efficacite de Detection en Fonction de l'Epaisseur des Echantillons: Determination de la Profondeur de Champ et Consequences pour le Couplage avec un Microscope Electronique en Transmission
Authors: Dhamelincourt P. , Delhaye M. , Truchet M. , da Silva E.
Published: May 2005

La faisabilité du couplage d'une sonde Raman avec une microsonde de Castaing ou un microscope électronique à transmission a été étudiée dès 1986. Dans ce dernier cas, l'épaisseur d'échantillon est très faible et une série de tests a été effectuée sur un matériau modèle, le polystyrène, afin de déterminer expérimentalement la profondeur de champ, ou résolution axiale, d'un microspectrométre Raman à détection multicanale utilisé dans les conditions d'éclairement de l'échantillon et de collection de la lumière diffusée aussi proches que possible de celles correspondant au systéme Raman implanté dans le microscope électronique. Les résultats obtenus montrent que la résolution axiale observée est de l'ordre de 2 μm et qu'un spectre Raman non résonnant de bonne qualité est encore obtenu pour une épaisseur d'échantillon de 50 nm et une résolution latérale de 0.7 μm soit 2 × 10−14 g de matériau analysé. Par des traitements numériques bien connus des signaux, il parait possible d'effectuer des mesures jusqu'à des épaisseurs de 10 nm.
Multimode analysis of depolarization ratio dispersion and excitation profiles of seven Raman fundamentals from the haeme group in ferrocytochrome c
Authors: Schweitzer‐Stenner Reinhard , Bobinger Ulrich , Dreybrodt Wolfgang
Published: May 2005

Experimental data for depolarization ratio dispersion (DPD) and resonance excitation profiles (REPs) with high spectral resolution (20 cm−1) are provided for seven Raman fundamentals in the region between 1150 and 1650 cm−1 of the haeme spectrum from ferrocytochrome c. They cover the resonant region of the Q‐band and the preresonant region of the B‐band. A self‐consistent analysis of the depolarization ratio dispersion (DPD) and resonance excitation profiles (REPs) of these Raman lines is carried out by explicit consideration of multimode mixing. This is achieved by first formulating the Raman tensor in Loudon's formulation to fifth order for each mode, thus restricting the contribution of the fifth‐order term to the vibration itself and omitting multimode contributions. By fitting this expression to the DPDs and REPs of each Raman mode, one obtains coupling parameters which in the next step are inserted into the fifth‐order term of each mode. Thus one takes account of their contributions to multimode mixing. To account for contributions of lower frequency modes, an effective ‘helping rest mode’ was added to the multimode contributions. This procedure yields satisfactory fits to all data sets. The respective fits to the DPD and REP of the oxidation marker line at 1363 cm−1 reproduce also the corresponding REP and DPD in the resonant region of the B‐band reported by Champion and Albrecht with a high degree of accuracy. The vibronic coupling parameters obtained are consistent with the weak coupling limit. Further, they confirm the validity of Gouterman's four‐orbital model for ferrocytochrome c.
Determination of aromatic composition of fuels by laser Raman spectroscopy
Authors: Clarke R. H. , Chung W. M. , Wang Q. , DeJesus S. , Sezerman U.
Published: May 2005

The application of Raman spectroscopy to the determination of the aromatic content of gasolines and aviation fuels is reported. Since aromatic components have very high Raman cross‐sections owing to large polarizability changes under laser excitation, bands from these components will dominate specific Raman spectral regions. It is expected, therefore, that Raman scattering will be a particularly useful approach to broadly characterizing the fuel hydrocarbon makeup for aromatic content and the properties of fuels which are influenced by aromatic content.
Raman and infrared spectra, conformational stability, barriers to internal rotation, ab initio calculations and vibrational assignment of dichloroacetyl fluoride
Authors: Durig J. R. , Bergana M. Mamula , Phan H. V.
Published: May 2005

The Raman spectra (3200‐10 cm−1) of dichloroacetyl fluoride (CHCL2CFO) of the gas, liquid (with qualitative depolarization ratios) and solid were recorded. The infrared spectra (3200‐30 cm−1) of the gas and solid were also obtained. All of these data indicate a trans/gauche equilibrium in the gas and liquid whereas only the gauche conformation remains in the solid. A complete vibrational assignment is proposed for both conformers based on the Raman depolarization data, infrared band contours, group frequencies and normal coordinate calculations. From the studies of the Raman spectra at various temperatures, the enthalpy difference between the stable conformers was determined to be 315 ± 68 cm−1 (0.90 ± 0.19 kcal mol−1) (1 kcal = 4.184 kJ) and 180 ± 4 cm−1 (0.51 ± 0.01 kcal mol−1) for the gas and liquid, respectively, with the trans conformer being more stable in the gas but the gauche conformer more stable in the liquid. These experimental results are compared to those obtained from ab initio Hartree‐Fock gradient calculations with the RHF/3‐21G* and RHF/6‐31G* basis sets, and to the corresponding quantities obtained for some similar molecules.
Silver colloid surface Raman spectra of phenylpropanolamine and its derivative
Authors: Li Ying‐Sing , Lee Arthur S. , Wang Yu
Published: May 2005

The silver colloid surface‐enhanced Raman scattering (SERS) spectrum of phenylpropanolamine (PPA) and the surface‐enhanced resonance Raman scattering (SERRS) spectrum of the PPA‐ninhydrin reaction product were studied. It was found that the spectral intensity varied with time, and the rate of the variation was related to the PPA concentration. From scanning electron microscopic photographs taken at different times, the SERS intensity appeared to be correlated with the coagulation of silver particles. Temperature was found to be another factor that would change the kinetic rate of the coagulation. Addition of potassium chloride served effectively to activate the surface‐enhanced effect and to reduce the time required to reach maximum intensity. The rate of activation was found to be dependent on the concentration.
Raman spectrum of Sr0.61Ba0.39Nb2O6
Authors: Wilde Richard E.
Published: May 2005

The Raman spectra of a single crystal of strontium barium niobate were recorded in the temperature range–193 to 140°C. The configurations studied were X(ZZ)Y, X(YZ)Y, X(YX)Y, Z(XX)Y, Z(YZ)Y and Z(XZ)Y. The behavior of integrated reduced intensities, band widths and band centers with temperature indicated that the ferro‐electric transition temperature was near 65°C. The Raman data were not consistent with a classical Landau transition. Disorder‐induced first‐order spectra were observed and attributed to the disordered nature of the crystal Evidence was found for a possible phase transition near 120°C.
Raman scattering of α‐toluenethiol adsorbed on silver sol
Authors: Lee Tae Geol , Kim Kwan , Kim Myung Soo
Published: May 2005

Surface‐enhanced Raman scattering (SERS) of α‐toluenethiol adsorbed on a silver surface has been investigated. The controversial vibrational assignment of the molecule was refined by comparing the SERS spectra with the ordinary Raman spectra of α‐toluenethiol, α‐toluenethiolate, benzyl chloride and their deuterated species. Based on the assignment and the SERS selection rule, it is proposed that α‐toluenethiol is adsorbed as a thiolate on silver via its sulphur atom with both the methylene group and benzene ring oriented approximately parallel to the metal surface.
Raman spectroscopic study on ZrO2–TiO2 using MoO3 as a molecular probe
Authors: Li Ying‐Sing , Lu Weijie , Collins W. Eugene
Published: May 2005

The surface interaction between ZrO2 and TiO2 in physical mixtures was studies using laser Raman spectroscopy (LRS). The characteristic peaks of ZrO2 disappeared after mixing ZrO2 and TiO2 with a loading ZrO2 of less than 25 wt.% and calcination at 773 K for 12 h. Surface polyhedrally coordinated Zr on TiO2 could not be detected by LRS. Therefore, MoO3 was used as a molecular probe to detect the nature of the interactions between ZrO2 and TiO2. The results revealed that ZrO2 could disperse on the surface of TiO2 and its interaction with TiO2 is different from that of MoO3 and TiO2.
Vibrational characterization and gas chemisorption of solid films and monolayers of dysposium and holmium bisphthalocyanines
Authors: Souto J. , Aroca R. , DeSaja J. A.
Published: May 2005

Evaporated thin solid films and Langmuir‐Blodgett monolayers of dysprosium and holmium bisphthalocyanine complexes were prepared and characterized using Raman scattering (RS), surface‐enhanced (resonance) Raman scattering, infrared and visible absorption spectroscopy. The spectroscopic evidence for molecular organization and molecular aggregation in the films is discussed. An empirical vibrational assignment of the observed fundamentals is proposed. Spectroscopic data on chemically oxidized films and films exposed to NOx(NO2/N2O4) were collected to determine the nature of the interaction between the MPc2 molecule and the NO2.
Rotational relaxation of nitrogen in argon: Collisional broadening of Q‐branch components in coherent Raman spectra of cooled gas
Authors: Kozlov D. N. , Pykhov R. L. , Smirnov V. V. , Vereschagin K. A. , Burshtein A. I. , Storozhev A. V.
Published: May 2005

A high‐resolution (0.003 cm−1) coherent anti‐Stokes/Stokes Raman spectrometer has been used for recording the resolved rotational structure of the Q‐branch of nitrogen in argon‐nitrogen mixtures. Spectra were obtained at pressures of 50‐760 Torr and temperatures of 295 and 140 K with the object of determining argon collisional‐broadening coefficients of nitrogen rotational lines. Semi‐classical calculations of these coefficients, employing a number of model potentials, were carried out. the experimental and theoretical data are compared and discussed.
Raman studies of structural phase transition in [NH2(CH3)2]3Sb2Cl9 (DMACA)
Authors: Miniewicz A. , Lefebvre J. , Jakubas R.
Published: May 2005

Tris(dimethylammonium) nonachlorodiantimonate (DMACA) is a ferroelectric with a transition temperature Tc = 242 K. Low‐frequency Raman spectroscopic studies were carried out on this crystal within the temperature range 100‐300 K to look for possible spectral changes resulting from the phase transition. A detailed analysis of frequencies, line widths and intensities was made through the phase transition in order to understand its nature. It follows from the analysis that pseudo‐spin‐phonon interactions of higher order are effective in this case.
Vibrational spectra and assignments of diethyl sulfide, 2‐chlorodiethyl sulfide and 2, 2′‐dichlorodiethyl sulfide
Authors: Christesen Steven D.
Published: May 2005

Raman and infrared (IR) spectra of diethyl sulfide (CH3CH2SCH2CH3), 2‐chlorodiethyl sulfide (ClCH2CH2SCH2CH3), and 2,2′‐dichlorodiethyl sulfide (mustard gas) (ClCH2 CH2SCH2CH2Cl) were measured and their vibrational frequencies were compared to calculated frequencies reported by Sosa et al. the calculated frequencies were used to make probable assignments of the vibrational bands to normal modes of the molecules. Raman depolarization ratios for diethyl sulfide and 2‐chlorodiethyl sulfide also aided in their vibrational assignments. Good agreement of the calculated frequencies with the experimental values was found except for the CS and CCl stretching frequencies, which were consistently calculated to be lower than the experimentally found values. The experimental spectra also provide evidence for the presence of more than one stable molecular conformation in the liquid phase for each of the three sulfides. This has been observed for diethyl sulfide in previous studies.
Surface‐enhanced near‐infrared fourier transform Raman scattering of tetrathiafulvalene adsorbed on silver powder
Authors: Nie Shuming , Yu Nai‐Teng
Published: May 2005

This report describes the use of an efficient and convenient silver substrate in the development of surface‐enhanced near‐infrared Fourier transform (FT) Raman scattering as a useful analytical technique that compliments the bulk FT‐Raman method. The SERS‐active material, prepared in the form of solid silver powder by means of chemical precipitation, is particularly well suited for surface Raman enhancement in the near‐IR region. To demonstrate the unique features of surface‐enhanced FT‐Raman, a detailed spectroscopic study of the charge‐transfer donor molecule tetrathiafulvalene (TTF) adsorbed on the silver powder is also reported. The advantages of near‐IR FT‐SERS over bulk FT‐Raman include the ability to analyze dilute solution samples, the acquisition of Raman spectra for near‐IR fluorescent compounds and new vibrational information concerning the mixed‐valence behavior of surface‐bound TTF molecules.
Raman and infrared spectra and photochemical behaviour of acetaldehyde isolated in matrices
Authors: Védova C. O. Della , Sala O.
Published: May 2005

As part of a general study on the behaviour of acetaldehyde as an atmospheric pollutant, the Raman and infrared spectra are presented of acetaldehyde isolated in argon and nitrogen matrices. Using the observed frequencies, the thermodynamic functions were calculated. By obtaining the vibrational spectra at low temperature, it was possible to assess the results of the photochemical studies that have been done in matrices with both argon and nitrogen gases. The main products in the photochemical decomposition of acetaldehyde under the conditions adopted are methane and carbon monoxide.
Preparation of substrates for surface‐enhanced Raman microprobe spectroscopy
Authors: Sutherland W. S. , Winefordner J. D.
Published: May 2005

The results obtained using a variety of new solid supports for the preparation of surface‐enhanced Raman‐active substrates via direct chemical reduction of silver salts and by vacuum vapor deposition of metallic silver are presented. These supports include two small pore size cellulose filter papers and frosted glass slides. These supports yield silver substrates with a much more uniform silver particle size and distribution than observed on previously used supports such as Whatman No. 1 and No. 5 filter papers. Results obtained using a solid silver membrane filter are also presented. These substrates provide metal particle morphology which is uniform on a submicrometer scale. This degree of uniformity is necessary for enhancing the reproducibility of SERS using a Raman microprobe since the area probed by this microprobe is 5–10 μm2. By using filter papers and glass slides, coupled with the vapor deposition and chemical reduction techniques, the resulting substrates are also fast, simple, and inexpensive, making them ideal candidates for routine analysis.
Raman spectra of Li(I), Na(I), K(I), Ba(II) and Cd(II) Salts of Uridine 5′‐monophosphoric acid
Authors: Carmona P. , Molina M. , Escobar R.
Published: May 2005

Raman spectra were obtained for crystalline Li(I), Na(I), K(I), Ba(II) and Cd(II) salts of uridine 5′‐monophosphoric acid. Assignments were made based chiefly on a comparison of the vibrational data observed for these compounds with those of uracil and D‐ribose‐5‐phosphate and on normal coordinate calculations. Some Raman spectral features, mainly in the 1420‐1350 and 700‐600 cm−1 ranges, seem to reflect the conformational structure of the uridine residue.
Electrochemical synthesis and in situ Raman spectroscopy of thin films of titanium dioxide
Authors: Arsov Lj. D. , Kormann C. , Plieth W.
Published: May 2005

Raman spectra of thin films of the TiO2 crystal modifications anatase and rutile are reported. The oxides are easily synthesized by electrochemical oxidation of titanium electrodes under controlled conditions. Evidence for the formation of a third crystal modification, possibly brookite, is presented.
Raman microscopy of a small uniaxial crystal: Tetragonal aspartame
Authors: Tsuboi Masamichi , Ikeda Teruki , Ueda Toyotoshi
Published: May 2005

A general method is presented for determining the shape and orientation of the Raman tensor of a molecule in a uniaxial crystal using a Raman microscope. First, equations are derived to connect the Raman tensor components (αxx, αyy, etc.) of a molecule to the Raman tensor components (αaa, αcc, etc.) of a crystal that is composed of molecules in a uniaxial arrangement, with an orientation specified by the two angles χ and θ. Next, a method is presented to obtain a correct set of values of the intensity ratios Iac/Iaa and Icc/Iaa from observed values of the intensity ratios measured with a Raman microscope. To augment the experimental data, the depolarization ratio ρ (for a completely random molecular orientation) is plotted as a function of r1 = αxx/αzz and r2 = αyy/αzz, so that a possible set of r1 and r2 values can be found from an observed value of ρ. The method has been applied to an aspartame IIA crystal (P41). A set of values of r1, r2, χ and θ has been determined for each of the following Raman fundamentals: 1741 cm−1 (ester CO stretch), 1667 cm−1 (amide I), 1275 cm−1 (amide III) and 1204 cm−1 (CCphenyl stretch), excited at 488.0 nm.
Raman spectroscopic investigation of polybromide‐containing functional polymers
Authors: Schnittke A. , Stegemann H. , Füllbier H. , Gabrusenoks J.
Published: May 2005

Solid polybromide‐containing functional polymers were obtained from basic anion‐exchange resins. The chloride or hydroxide anions of the commercial resins were exchanged by bromide, then dried under anaerobic conditions and allowed to react with a gaseous bromine phase. The formation of linear, slightly asymmetric tribromides was proved by Raman and far‐IR spectroscopy. The tribromide spectra are characterized by the symmetrical stretching vibration ν1 at about 160 cm−1 and the antisymmetric stretching vibration ν3 at about 200 cm−1. If the Br2: Br− molar ratio is greater than 1 an additional band could be observed at about 255 cm−1. This band is assigned to the stretching vibration of coordinated bromine. It is shifted in the direction of free bromine at about 300 cm−1 with increasing bromine content in the functional polymers. According to the spectroscopic results, the anion structure in amorphous polybromide‐containing functional polymers can be explained by tribromide ions and bromine molecules interacting with the tribromide. The thermal instability of higher polybromides was also proved spectroscopically.
Raman and infrared spectra of solid dichlorofluoromethane
Authors: Lefebvre J. H. , Anderson A.
Published: May 2005

Raman and infrared spectra of solid dichlorofluoromethane were recorded in both the internal and lattice mode regions at 20 and 80 K. The lattice spectra are consistent with a non‐centrosymmetric unit cell containing at least four molecules. All nine internal modes are observed, and their multiple components are interpreted in terms of crystal field effects and isotopic splittings.
Theoretical investigations of discrete resonance Raman scattering in H2 via intermediate B, C states
Authors: Banerjee Sima , Bhattacharyya S. S. , Saha Samir
Published: May 2005

Discrete resonance Raman scattering (DRRS) from the ground X1Σg+(νg = 0, Jg = 0‐2) state of H2 via excited intermediate states B1Σu+(νi = 0‐3, Ji = 0‐3) and C1Πu(νi = 0‐3, Ji = 1‐3) was studied theoretically, applying the reduced density operator formalism. The Raman Spectra for the pure rotational, fundamental and higher overtones are presented. The intensities of the Raman lines for O, Q and S branches were calculated using thermal Boltzmann factors for vibrational‐rotational distribution at room temperature (300 K). The calculated DRRS cross‐sections are found to be many orders of magnitude larger than normal (non‐resonance) Raman cross‐sections for H2 or continuum resonance Raman cross‐sections for molecular ions such as HD+.
Solution‐phase vibrational relaxation studies in N,N‐dimethylacetamide
Authors: Purkayastha Anusree , Kumar Kamal
Published: May 2005

Vibrational relaxation studies in N,N‐dimethylacetamide revealed that the hydrodynamic and dispersion forces play a significant role in the line broadening of the CO stretching vibrational band. The non‐coincidence effect was also examined in the light of dielectric screening due to different environmental conditions.
Absolute Raman pair cross‐section for the πu mode in supercritical carbon dioxide
Authors: Baglin F. G. , Hacura A. , Yoon J. H.
Published: May 2005

The absolute Raman cross‐section was measured for the πu mode of supercritical carbon dioxide at 50 and 75°C over five densities. These measurements clearly show that a dimeric species is responsible for the quadrupole induced dipole (QPID) Raman spectral activity of the πu(ν2) transition in carbon dioxide. This result is in accord with earlier predictions by Amos et al.
Raman scattering and scanning electron tunnelling studies of metal liquid‐like films produced from silver and gold sols
Authors: Bell Steven E. J. , McGarvey John J. , Rigby Stephanie J. , Walmsley D. G.
Published: May 2005

Surface‐enhanced Raman scattering (SERS) excited at several visible wavelengths and recorded using a cooled charged‐coupled device detector is reported from the mobile, interfacial, liquid‐like metal films (MELLFs) formed when solutions of metal complexes or pyridine in chlorocarbon solvents are mixed with aqueous sols of silver or gold. MELLF formation has not previously been reported for gold sols or for pyridine as stabilizer. Comparison of the spectra for the MELLFs formed from individual metal complexes and from 50:50 mixtures show that the spectral patterns observed for the latter are distinctive and are not generally equivalent to the sum of the spectra associated with the individual complexes, in contrast to the situation observed for sols where the individual spectra do appear to be additive. Raman scattering from both gold and silver MELLFs is readily observed at excitation wavelengths in the red, around 750 nm, but at 514 nm only that from silver films is detectable. These findings are considered in terms of particle size and absorption band intensities. A preliminary study of the film surface topography and particle size was carried out by scanning tunnelling electron microscopy (STM) of Ag MELLFs deposited on gold‐coated mica substrates. Computer‐processed images of the STM data show the presence on the film surface of finger‐like bars, 200–400 nm long with approximately square cross‐section, 40–60 nm side, together with other smaller cuboid features. The implications of these findings in relation to SERS are briefly considered.
Surface‐enhanced resonance Raman scattering of a NO2‐bisphthalocyanine adduct in Langmuir‐Blodgett monolayers
Authors: Souto J. , Aroca R. , Desaja J. A.
Published: May 2005

Langmuir‐Blodgett (LB) monolayers of dysprosium and holmium bisphthalocyanine complexes (DyPc2 and HoPc2) were prepared at 10°C and transferred to glass slides coated with gold island films. Surface‐enhanced resonance Raman scattering (SERRS), and visible absorption spectrometry were used to monitor the interaction between the LB monolayer and NOx (NO2‐N2O4) gas. It is shown that the absorption and inelastic scattering spectra of LB are sensitive tools to monitor the interaction between the MPc2 molecule and the NO2, allowing the spectral properties of the adduct formed by chemisroption to be determined.
SERS and Fourier transform SERS studies of the hexacyanoferrate(III)‐hexacyanoferrate(II) couple on gold electrode surfaces
Authors: Lowry R. B.
Published: May 2005

Surface‐enhanced Raman spectroscopy (SERS) and its Fourier transform (FT) variant were used to study the hexacyanoferrate(III)‐hexacyanoferrate(II) couple at the surface of gold electrodes. The effects of potential, Fe(CN) concentration and base electrolyte (KCl) concentration were measured, and point to distortion of the Fe(CN) ion on the surface of the electrode. The Fe(CN) ion was found not to be strongly adsorbed when a base electrolyte concentration of > 10 mM was used, but the strong adsorption of the Fe(CN) ion was demonstrated. The increased resolution that is possible when using the FT‐SERS technique allows for the partial resolution of bands in the CN stretching region, and thus the construction of a model for the hexacyanoferrate(III) system.
Raman and far‐infrared spectra, conformational stability, barriers to internal rotation, vibrational assignment and ab initio calculations of 2,3‐dicholoropropene
Authors: Durig D. T. , Guirgis G. A. , Durig J. R.
Published: May 2005

The far‐infrared spectrum (375 to 30 cm−1) of gaseous 2,3‐dichloropropene, CH2C(CH2Cl)Cl, was recorded at a resolution of 0.06 cm−1. The fundamental asymmetric torsional mode is observed at 91.9 cm−1 with eight excited states falling to low frequency for the s‐cis (chlorine atom eclipsing the double bond) conformer. For the higher energy gauche conformer, the asymmetric torsion is estimated to be near 85 cm−1. Utilizing the s‐cis torsional frequency, the gauche dihedral angle and the enthalpy difference between conformers, the potential function governing the interconversion of the rotamers was calculated. The determined potential function coefficients are V1 = 1047 ± 96, V2 = −619 ± 68, V3 = 1216 ± 50 and V4 = 26 ± 22 cm−1, with an enthalpy difference between the more stable s‐cis and gauche conformers of 245 ± 30 cm−1 (0.70 ± 0.09 kcal mol−1). This function gives values of 1035 ± 10 cm−1 (2.96 ± 0.03 kcal mol−1), 2015 ± 150 cm−1 (5.76 ± 0.43 kcal mol−1) and 787 ± 10 cm−1 (2.25 ± 0.03 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 liquid at 1633 cm−1 (gauche) and 1649 cm−1 (s‐cis) as a function of temperature, the enthalpy difference is found to be 334 ± 39 cm−1 (0.95 ± 0.11 kcal mol−1), but now with the gauche conformer more stable. Also, the more polar gauche conformer remains in the crystalline solid. The Raman spectrum of the gas was recorded from 3500 to 70 cm−1 and, utilizing these data and the previously reported infrared data, a complete vibrational analysis is proposed for both conformers. The conformational stability, barriers to internal rotation, fundamental vibrational frequencies and structural parameters which were determined experimentally are compared to those obtained from ab initio Hartree—Fock gradient calculations employing both the 3‐21G* and 6‐31G* basis sets and to the corresponding quantities for some similar molecules.
Raman and infrared spectra of solid hydrogen selenide
Authors: Paldus B. A. , Schlueter S. A. , Anderson A.
Published: May 2005

Raman and infrared spectra of solid H2Se at temperatures between 85 and 20 K are reported and interpreted. The broad peaks observed in the spectra of phase II are characteristic of an orientationally disordered crystal, whereas the multiple components of the internal modes and rich lattice spectra found for phase III are indicative of an ordered structure. The unit cell for this phase is probably centrosymmetric and contains at least four molecules. Plausible assignments for all observed spectroscopic features are proposed.
Spectra and structure of organophosphorus compounds. XLVIII—Raman and infrared spectra, conformational stability, vibrational assignments and ab initio calculations of dimethyl(methylthio)phosphine
Authors: Durig J. R. , Smith David F. , Barron D. A. , Harlan R. J. , Phan H. V.
Published: May 2005

The Raman spectra (3200–10 cm−1) and infrared spectra (3200–50 cm−1) of dimethyl(methylthio)phosphine, CH3SP(CH3)2, and dimethyl(methyl‐d3‐thio)phosphine, CD3SP(CH3)2, in the gas and solid forms were recorded. Additionally, the Raman spectra of the liquids were recorded and qualitative depolarization ratios measured. All 36 of the normal modes were assigned and the asymmetric torsion was observed in the far‐infrared spectrum of gaseous CH3SP(CH3)2 at 75 cm−1. From a comparison of the vibrational spectra obtained for the fluid phases with those obtained for the amorphous and annealed solids, it is concluded that the molecule exists as a mixture of the cis and trans conformers in the fluid phases with the trans conformer being the more stable form in the liquid and the only one present in the spectra of the annealed solid. However, for the vapor state the cis conformer is the more stable form. The enthalpy difference between the cis and the trans conformers was determined from a variable‐temperature study of the Raman spectrum of the liquid to be 199 ± 8 cm−1 (569 ± 23 cal mol−1). A complete vibrational assignment is proposed which is supported by a normal coordinate calculation obtained from the force fields calculated with the ab initio RHF/3–21G* basis set. Full geometry optimizations were carried out with the 3–21G* and 6–31G* basis sets for the transition state to determine the barriers to internal rotation about the CH3SP bond. All of these results are compared with corresponding data for several other organophosphorus compounds.
Vibrational spectrum of Zn2 VO(PO4)2
Authors: Baran Enrique J. , Lii Kwang‐Hwa
Published: May 2005

The infrared and laser Raman spectra of Zn2 VO(PO4)2 were recorded and are briefly discussed with the aid of a factor group analysis. Some interesting aspects related to the strongly condensed nature of the phosphate groups and to the characteristics of the VO bonds in this structure are also considered.
Vibrational spectra, thermodynamic functions and barriers to internal rotation for isomeric trifluoromethylbenzoyl chlorides
Authors: Shanker R. , Yadav R. A. , Singh I. S. , Singh O. N.
Published: May 2005

The polarized Raman spectra (50–4000 cm−1) and IR spectra (180–4000 cm−1) of o‐, m‐ and p‐ trifluoromethylbenzoyl chlorides were recorded and all the 45 (30a′ + 15a") normal modes of vibration were assigned assuming Cs symmetry. Consistent assignments for the internal modes of the COCl and CF3 groups are proposed. Thermodynamic functions were computed and barriers to internal rotations for the COCl and CF3 tops were determined, using the assigned vibrational frequencies and assumed structural parameters for the three isomers.
Raman and infrared study of structural phase transitions in (NH4)3H(SeO4)2 and (ND4)3D(SeO4)2
Authors: Raimbault G. , Romain F. , Lautié A.
Published: May 2005

The Raman and infrared spectra of (NH4)3H(SeO4)2 and (ND4)3D(SeO4)2 were investigated between 20 and 400 K in the 4000–10 cm−1 frequency range. Five crystalline phases were characterized spectroscopically and structural information was obtained by comparison with results previously obtained on sulphate analogues. Phase III at room temperature is strongly disordered, mainly as regards the ammonium ions, and a decrease in temperature leads to a progressive ordering; however, parent and deuterated compounds show different phase sequences. Only the ferroelectric phase V shows the spectra characteristic of a fully ordered crystal. The mechanism of phase transitions, involving motions of NH4+ and selenate entities, and the behaviour of the strong OH…︁O hydrogen bond, present in the asymmetric (SeO4HSeO4)3− dimers, are discussed.
Vibrational spectra and conformation of 1‐chloro‐4‐fluorobut‐2‐yne and ab initio calculations on 1,4‐dihalobut‐2‐ynes
Authors: Karlsson A. , Klaeboe P. , Nielsen C. J.
Published: May 2005

Raman spectra were recorded in the 3200‐5 cm−1 range for 1‐chloro‐4‐fluorobut‐2‐yne as a liquid at various temperatures and as amorphous and different crystalline solids at low temperature. In the liquid, the Raman spectra showed broad, asymmetrical band shapes as previously reported for other 1,4‐dihalobut‐2‐ynes. Additional IR and far‐IR spectra were obtained of the liquid, vapour, amorphous and crystalline solids at low temperature, and of the compound isolated in argon and nitrogen matrices at 13 K. The vapour and liquid spectra were interpreted in terms of a low barrier to internal rotation and the crystal spectra of a single conformer, gauche. The unusual band shapes in the low‐frequency Raman spectra of the 1,4‐dihalobut‐2‐ynes are discussed and are reproduced fairly well by a simple model of a molecule exhibiting nearly free internal rotation. The agreement between the observed and calculated spectra is good for all the molecules studied when ab initio potentials are applied in the model calculations. Temperature effects in the Raman spectra of liquid 1‐chloro‐4‐fluorobut‐2‐yne can also be derived from the model. Internal rotation in 1,4‐difluoro‐, 1,4‐dichloro‐, 1‐chloro‐4‐fluoro‐, 1,4‐dibromo‐ and 1,4‐diiodobut‐2‐yne was studied with the aid of ab initio calculations. The barriers were found to be low and decreasing through the series from 1,4‐difluoro‐ to 1,4‐diiodobut‐2‐yne accompanied by an increase in the equilibrium dihedral angle, XCCCCY, from 101° in 1,4‐difluorobut‐2‐yne to 180° in 1,4‐diiodobut‐2‐yne. The systematic variations through the series were correlated with the local dipole moments of the halomethyl groups and the electronegativities of the halogen substituents.
Vibrational spectra of LiNH3OHSO4 and LiND3ODSO4
Authors: Pillai V. P. Mahadevan , Pradeep T. , Suresh G. , Nayar V. U.
Published: May 2005

Infrared and Raman spectra of LiNH3OHSO4 and LiND3ODSO4 were recorded and analysed. Bands were assigned on the basis of SO4, NH3 and OH vibrations. The symmetric stretching mode in the deuterated compound is found to be at higher frequencies, indicating the existence of strong hydrogen bonds in LiNH3OHSO4. The SO4 ion is distorted in the crystal. A, B and C bands are observed in the OH stretching region, also showing the formation of strong hydrogen bonds.
Resonance Raman enhancement of the oxo‐bridged dinuclear iron center: Vibrational modes in iron(III) physiological‐type porphyrin complexes
Authors: Brémard C. , Kowalewski P. , Merlin J. C. , Moreau S.
Published: May 2005

Oxo‐bridged dinuclear iron(III) complexes of two physiological‐type prophyrins, (DPDEFe)2O and (PPDEFe)2O (where DPDE = deuteroporphyrin dimethyl ester and PPDE = protoporphyrin dimethyl ester), were investigated using resonance Raman and infrared spectroscopy. The assignment of the porphyrin vibrational modes was performed using polarization measurements and previous studies concerning the corresponding mononuclear iron(III) complexes, (DPDEFe)Cl, (PPDEFe)Cl, and related compounds. The assignment of the FeOFe axial bridge vibrational modes of the two μ‐oxo complexes investigated and the synthetic analogue (TPPFe)2O (where TPP = tetraphenylporphyrin) was made with the help of 18O substitution. The dependence of the frequencies vs and va on the FeOFe angle for (TPPFe)2O is in good agreement with the angle value previously determined by x‐ray diffraction data. The values of the FeOFe angle in (DPDEFe)2O and (PPDEFe)2O were estimated to be close to 160° and 170°, respectively. The excitation profiles (351.1–647.1 nm) of the porphyrin core marker bands for all the μ‐oxo complexes studied are in good agreement with the expected general trends of the resonance enhancement with moderate vibronic coupling. However, for the μ‐oxo physiological‐type porphyrin complexes, the v4 marker band exhibits and unexpected strong enhancement maximum near the maximum found in the excitation profile of the va and vs (FeOFe) modes. These enhancement maxima tend to correspond to a minor oxo → Fe(III) charge‐transfer band in the electronic absorption spectra. A mixing of several electronic levels under low symmetry may be responsible for this enhancement phenomenon.
Surface‐enhanced Raman spectroscopic study of amsacrine and amsacrine–DNA interactions
Authors: Barton Thomas F. , Cooney Ralph P. , Denny William A.
Published: May 2005

Surface‐enhanced Raman scattering (SERS) spectroscopy has been employed to study the interaction of intercalating ligands with DNA. SERS was used to obtain spectra of acridine, aminoacridine, the 9‐anilinoacridine amsacrine and related compounds at associated solution concentrations down to 1 μM. A major advantage of SERS was the near absence of fluorescence normally inherent in solution spectra of these compounds. SERS spectra of amsacrine–DNA complexes at various ligand/base pair ratios showed free ligand concentrations consistent with those calculated from the binding constant, and showed that the less strongly interacting acridine was largely unbound even at high ligand/base pair ratios.