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Molecular structure and vibrational frequencies of 3-glycidoxypropyltrimethoxysilane (GPTMS) have been investigated by density functional theory (DFT) calculations using Becke’s three-parameter exchange functional combined with Lee–Young–Parr correlation functional (B3-LYP) and standard basis set 6-311++G(d,p). In order to reveal some possible conformations of GPTMS, potential energy scan has been performed in three dihedral angles SiCCC, CCCO and OCCO. The calculations predict the existence of seven different conformations. Raman and IR spectra of liquid samples were recorded and complete assignment of the observed vibrational bands of GPTMS molecule has been proposed. Temperature dependence of Raman spectra between 203 K and 293 K was examined and vibrational modes characteristic for different conformers were detached.

Alteration minerals dickite and kaolinite were detected in two hydrothermal Pb-Zn-Ag sulphide deposits in the northern Kosovo region. Dickite is associated with skarn mineralization in the Trepča (Stari Trg) deposit and kaolinite occurs in vein sulphide parageneses in the Crnac deposit. The mineralogical characteristics of dickite and kaolinite were determined by X-ray powder diffraction, Raman spectroscopy and scanning electron microscopy with EDS detector. Fluid-inclusion microthermometry and ion chromatography of leachates provided information on theP-T-Xconditions of the genesis of dickite at Trepča. It was formed at temperatures between 290 and 330ºC and pressures between 12 and 60 MPa from a fluid with salinity in the range 6–8.5 wt.% NaCl eq. and pH

Low wavenumber polarized Raman spectra of aminopropylsilanetriol (APST) polymer deposited on PVC substrate were measured in the temperature range from 300 K to 78 K. In the low wavenumber Raman spectra of these samples a very strong Bose band was observed. The best results in modeling the low wavenumber Raman spectra were achieved with the exponential correlation function of disorder Gdis(ν) = exp (−r/Rc)using three contributions: transversal and longitudinal acoustic phonons and molecular vibration. Results suggest medium range ordered ladder structure, stacked in layers with different orientations of ladders.

Raman spectrum of aminopropylsilanetriol (APST) in gas phase has been recorded at room temperature in macro chamber utilizing two-mirror technique over the sample tube. Unlike predominantly trans molecular conformation in condensed phase, the spectra of vapor show that the molecules are solely in gauche conformation with intramolecular hydrogen bond N···HO which reduces the molecular energy in respect to trans conformation by 0.152 eV. The assignment of the molecular spectra based on the DFT calculation is presented. The strong vibrational bands at 354 cm(-1), 588 cm(-1) and 3022 cm(-1) are proposed for verifying the existence of the ring like, hydrogen bonded structure. Special attention was devoted to the high frequency region, where hydrogen bond vibrations are coupled to stretchings of amino and silanol groups.

A Time-of-Flight detector (TOF), with a technique based on plastic scintillators and finemesh photomultipliers, has been added to the CDF-II experiment. The main physics motivation is to improve neutral B meson flavor determination by K± identification. The expected time resolution is 100 ps, which provides at least two standard deviations separation between K± and π± for momenta p < 1.6 Gev/cand better than 1.2 standard deviations separation over all momenta when combining TOF identification with dE/dx identification using the new drift chamber.

L'acide terephtalique solide existe sous deux formes polymorphes tricliniques. Des etudes de spectroscopie Raman ont ete effectuees en vue de reconnai←tre la presence de la forme I et/ou de la forme II dans l'echantillon

Motivations, design, performance and upgrade of the CDF Silicon Vertex Trigger are presented. The system provides CDF with a powerful tool for online tracking with offline quality in order to enhance the reach on B-physics and large P t-physics coupled to b quarks.

Raman spectroscopy is applied to the study of the structure of polycrystalline silicon films. The analysis of the transversal optical phonon Raman line shows its complex structure consisting of two dominant contributions, centered at about 519 and 517 cm(-1) and attributed to two dominant groups of grains with different size. The profile of this Raman line is demonstrated to give deeper information about the film morphology, directly influenced by the deposition temperature in terms of the ratio of amorphous to crystalline phases, as well as the grain-size distribution, and the film stress. (C) 1999 American Institute of Physics

Edge-defined film-fed grown polycrystalline silicon sheets, grown with one face exposed to oxidizing CO gas added to the inert Ar atmosphere, were studied. Interaction of CO with molten silicon surface during growth produced SiC-like structures in a thin layer on the surface exposed to CO. Infrared spectroscopy results suggest that this layer is constituted of good quality SiC ; however, Raman and x-ray photoelectron spectroscopy showed that it consists of Si1− xCx in the form of small crystallites mixed with C- and O-rich silicon. Journal of Applied Physics is copyrighted by The American Institute of Physics.

The Raman spectra of glycine molecule have been studied for solid state, as well as for ordinary and heavy water solutions. Some new bands were observed, causing our assignment to differ from previous two and yet reconciling them both. In the concentration dependence study unusual downshift and intensity change of certain bands were noticed. This is explained by assumption of the Fermi resonance model and a weak hydrogen bonding arising between glycine and solvent molecules.

In the present study, pure poly(dimethylsiloxane) (PDMS) polymer and PDMS-detonation nanodiamond (PDMS-DND) composite with 1wt.% of DND were irradiated under vacuum at room temperature with a 2 MeV proton beam with fluences in the 1013 to 1015 cm-2 range. Modification of the structures and properties of the pure polymer and the nanocomposite material were monitored as a function of proton fluence. Specifically, the vibrational dynamics of pure PDMS and PDMS-DND nanocomposites, both unirradiated and irradiated samples, were investigated using Raman and Fourier transform infrared spectroscopy (FTIR). The Raman and FTIR spectra of the PDMS and PDMS-DND composites exhibit an overall reduction in intensity of all vibrational bands of the irradiated samples. The changes in relative intensities of the characteristic vibrational bands as a function of irradiation fluence indicate that cleavage of the backbone (Si-O-Si) PDMS chains was most pronounced. Importantly, structural degradation of PDMS-DND composites takes place at an order of magnitude higher fluence than for pure PDMS, indicating the potential of using DND-based polymer composites for application in high radiation environments. The appearance of strong photoluminescence (PL) following irradiation was more pronounced for PDMS-DND composites as compared to pure PDMS.

Les spectres montrent que les proprietes optiques de ces echantillons manifestent plus nettement leur structure a defauts que les differentes masses atomiques des constituents. Les positions des pics sont peu sensibles a la composition de l'echantillon

Lattice vibrations of acenaphthene have been calculated using the rigid-molecule approximation. The spectrum has been completed with two new bands observed at low temperature. The intensity of some of the observed Raman bands has been discussed.

Librational and translational modes of crystalline imidazole are active in the low-frequency Raman spectrum of this crystal. Librational modes have been assigned by the oriented gas model, which is particularly suitable for calculating the intensity matrices. Translational modes contain intermolecular NH⋯N hydrogen-bond vibrations. The assignment of translational modes has been made assuming two types of motion: intrachain and interchain. This separation of translation modes makes it possible to assign intermolecular hydrogen-bond vibrations in the imidazole crystal.

The application of pulsed electric fields (PEF) and pulsed electric currents (PEC) to superconductors based upon Y-Ba-Cu-O compound is promising since we deal with highly deformed perovskites. If PEF is applied in mixed phase Y 1.2 Ba 0.8 CuO 4 before sintering simultaneously with uniaxial compression the states of low resistance can be induced up to 210 K. The onset to low resistance state takes place at 280 K and in most significant cases the ratio of low/high resistance is less than 1/2000. Raman data, X-ray measurements and susceptibility data support an opinion that we are dealing with new phase not known in the recently published sequence of yttrium oxides.

Raman and infrared spectroscopic studies of benzoic acid dimers and crystals have been made. Molecular and crystal normal modes have been calculated. An assignment of the observed spectra has been proposed and some specific modes discussed.

Vibrational spectroscopic measurements combined with the lattice statics and lattice mod es calculations have been applied in order to derive the most probable structure of the low temperature (stable) phase V of thiophene (below 112 K). The far infrared spectrum has been recorded from 135 to 30 cm? of this phase of thiophene at 20 K. The low frequency Raman spectrum from 150 to 10 cm" has also been record ed for the phase V at 35 K. From the fact that there is coincidence between lattice mode frequencies observed in the infrared and Raman spectra, one can exclude centrosymmetric space groups. The observations of 20 lattice modes in the Raman spectrum and 14 modes in the FIR spectrum eliminate the possibility of tetragonal symmetry, but the data are consistent with orthorhombic symmetry with the unit cell containing 4 molecules on Cl sites. In spite of the glassy-like transition observed for this phase at 42 K, both spectra bear striking resemblance to the typical low frequency spectra of molecular crystals. Therefore, it is assumed, for the purposes of the static and dynamic studies, that the thiophene in phase V can be considered as an ideally ordered crystal. Calculations of the lattice energy and lattice mode frequencies, based on the atom-atom potential, appear to be most consistent with space group Pca2l (C2v5) which is in agreement with most of the earlier predictions made for the structure of the thiophene phase V. The Raman spectrum of the metastable phase II2 is also given.

We have observed a low resistance state up to 210 K in a mixed system of the nominal composition Y1.2Ba0.8CuO4-δ prepared under simultaneous action of a pulsed dc electric field up to 30 kV/cm and uniaxiakl pressure of ≈ 1.5 GPa. An onset of a decrease of the resistance at 281 K is observed in repeated cycles and is accompanied by diamagnetism in the temperature interval 150 K

The medium-resolution Raman spectrum of benzoic acid vapour has been recorded. Comparison of the high-frequency spectrum with the internal spectra of substituted and similar molecules indicates that previous assignments of the spectra should be revised. Three possible explanations are proposed for the broad feature observed at very low frequencies. Two of them lead to the conclusion that there is a very low barrier for hindered rotation around the CC bond connecting the carboxylic group with the phenyl ring.

Une etude du spectre Raman de basses frequences est faite en utilisant l'excitation par un laser a gaz He-Ne. Une methode de mesure des intensites pour les spectres des cristaux est proposee. Les mesures d'intensite sont comparees avec les intensiites calculees par le modele de gaz oriente.