Search results for "Vibrational Spectra"
showing 10 items of 31 documents
Aminoacid zwitterions in solution : Geometric, energetic, and vibrational analysis using density functional theory-continuum model calculations
1998
Glycine and alanine aminoacids chemistry in solution is explored using a hybrid three parameters density functional (B3PW91) together with a continuum model. Geometries, energies, and vibrational spectra of glycine and alanine zwitterions are studied at the B3PW91/6-31+G∗∗ level and the results compared with those obtained at the HF and MP2/6-31+G∗∗ levels. Solvents effects are incorporated by means of an ellipsoidal cavity model with a multipolar expansion (up to sixth order) of the solute’s electrostatic potential. Our results confirm the validity of the B3PW91 functional for studying aminoacid chemistry in solution. Taking into account the more favorable scaling behavior of density funct…
Über polygermane
1980
Abstract A complete series of 5-membered heterocycles (Ph 2 Ge) 4 X with X = O, S, Se and Te has been prepared and investigated by mass spectra, 13 C NMR spectra and vibrational spectra. The 13 C signals of the phenyl groups in the compounds (Ph 2 Ge) 4 X were compared with the related values in the homocycle (Ph 2 Ge) 5 . Frequency values for the symmetrical and asymmetrical stretching vibrations of the units GeGeGe and GeXGe are given. The crystal structure of the compound (Ph 2 Ge) 4 S has been determined and refined to a R of 0.051. The 5-membered ring Ge 4 S exhibits envelope conformation.
Synthesis and low-frequency vibrational spectra of some halo- and pseudohalo-diphenylantimonates(V)
1976
Abstract The syntheses of diphenylantimonates(V) of the type M(I) [PH 2 XbX 4 ] (M(I) = PH 4 As; X = F, Cl, Br, N 3 , NCS; X 4 = Cl 3 Br, Cl 3 N 3 ) are described. Far-Ir spectra of these compounds and of previously synthesized M(I) [Ph 2 SbCl 3 X] species (M(I) = Me 4 N; X = Cl, Br, N 3 ; M(I) = Ph 4 As; X = NCS) are reported. Raman spectra of tetrafluoro and tetrachloro salts are also given. Vibrational data are interpreted in terms of the presence of solid of trans -Ph 2 SbX 4 - species and assignments of skeletal modes are suggested.
Theoretical studies of isomers of C 3 H 2 using a multiconfigurational approach
2000
The C3H2 isomers are important molecules in interstellar space. An understanding of their electronic structure can contribute significantly to the interpretation of interstellar spectra. In a theoretical study of the C3H2 isomers a multiconfigurational treatment is of interest because many of the isomers are carbenes or diradicals. We present such an investigation of all possible C3H2 isomers. The most important features of their electronic and vibrational spectra are calculated. Earlier theoretical studies are reviewed and it is shown that the present study yields the same order of stability for the singlet and triplet states as most previous studies.
From atomic to molecular Bose-Einstein condensates: a physically realizable term-crossing model for cold atom association
2010
Using an exact third-order NL di®erential equation for the molecular state probability, we develop a variational approach which enables us to construct highly accurate analytic approximations describing time dynamics of the coupled atom-molecular system in each of the interaction regimes. We show that the approximation describing time evolution of the molecular state probability both in the weak interaction limit and in the large detuning regime of the strong interaction limit can be written as a sum of two distinct terms; the ¯rst one, being a solution to a limit ¯rst-order NL equation, e®ectively describes the process of the molecule formation while the second one, being a scaled solution…
Vibrational spectra and force constants of symmetric tops
1983
The infrared spectrum of H3SiI in the 800–1050 cm-1 region has been recorded with a resolution of 0·04 cm-1 and rotationally analysed. Features related to the Fermi resonance between v 5 and v 3 + v 6 and to the Coriolis x, y resonance between v 2 and v 5 have been explained, and a set of vibration-rotation parameters for the three bands has been determined by least-squares calculations, σ(J, K) = 9·4 × 10-3 cm-1. The Fermi resonance matrix element |W 356| is found to be 3·7859(7) cm-1 and the vibrational frequencies are v 2 0 = 904·551(1), v 5 0 = 941·0746(8) and (v 3 + v 6)0 = 953·688(3) cm-1. The anharmonicity constant, x 36 = -1·745(9) cm-1, has been determined. Comparison is made with …
High Resolution Study of the v1 + 2v2 −v2 and 2v2 + v3 − v2 ”Hot” Bands and Ro-Vibrational Re-Analysis of the v1 + v2/v2 + v3/3v3 Poliad of the SO2 M…
2010
The main goal of the present study was to analyse rotational stuctures of two excited vibrational states, (120) and (021). Because both the band, v1+2v2 and 2v2+v3 one are extremally weak, a special efforts were faired to record very weak hot bands, v1+2v2−v2 and 2v2+v3−v2.Both of those bands are located in the region of considerably more stronger combinational bands, v1 + v2 and v2 + v3. On that reason, as the first step of analysis, we made assignments of transitions belonging to these v1 + v2 and v2 + v3 bands. As the result of analysis, we were able to assign three times more transitions to the bands v1 + v2 and v2 + v3 than it was known in the before literature. After "cleaning" the ex…
Über gemischte bindungen in der IV. Hauptgruppe
1984
Abstract The reaction of Ph 3 PbLi with Ph 3 SnCl or Ph 3 GeCl gives Ph 3 PbSnPh 3 and Ph 2 PbGePh 3 , respectively; there is no reaction with Ph 3 SiCl. Ph 3 SiLi reacts with Ph 3 PbCl to form a regular 1 : 1 Pb 2 Ph 6 · Si 2 Ph 6 phase. The compounds have been investigated by mass, NMR and vibrational spectra: 207 Pb NMR chemical shifts with respect to PbMe 2 −79.8 (Pb 2 Ph 6 ), −256.5 (Ph 3 PbSnPh 3 ), −271.5 ppm (Ph 3 PbGePh 3 ); stretching vibrations 112 (PbPb), 125 (PbSn), 138 cm −1 (PbGe). The crystal structures have been determined and refined to R = 0.061 (Ph 3 PbSnPh 3 , −40°C), 0.053 (Ph 3 PbGePh 3 , −50°C), 0.068 (Pb 2 Ph 6 · Si 2 Ph 6 , 20°C); bond lengths 285 (PbPb),…
High-resolution FTIR spectra analysis of sulfur dioxide isotopologues
2019
In this thesis we considered the spectral properties of the sulfur dioxide. The experimental FTIR spectra of numerous sulfur dioxide isotopologues, 32S16O2, 34S16O2, 32S18O2 and 32S16O18O, were first recorded in the regions of fundamental, «hot», combination and overtone bands. The wide variability of the experimental conditions gave possibility to observe and identify for the first time transitions be¬ longing to the following of ro-vibrational bands: 3v2, 3v2 - v2, 2v2 - v2 bands of 32S16O2; 2v2 - v2 band of 34S16O2; v1 + v2, v2 + v3, v1 + v3, 2v1, 2v3 bands of 32S18O2; v1, v3, 2v1, v1 + v3, 2v3 bands of 32S16O18O. The inverse spectroscopic problems were solved for the studied states with…
Optical and Vibrational Spectra of CsCl-Enriched GeS2-Ga2S3 Glasses
2016
Optical and FTIR spectroscopy was employed to study the properties of 80GeS2-20Ga2S3-CsCl chalcohalide glasses with CsCl additives in a temperature range of 77–293 K. It is shown that CsCl content results in the shift of fundamental absorption edge in the visible region. Vibrational bands in FTIR spectra of (80GeS2-20Ga2S3)100 − х (СsCl) x (x = 5, 10, and 15) are identified near 2500 cm−1, 3700 cm−1,, around 1580 cm−1, and a feature at 1100 cm−1. Low energy shifts of vibrational frequencies in glasses with a higher amount of CsCl can be caused by possible thermal expansion of the lattice and nanovoid agglomeration formed by CsCl additives in the inner structure of the Ge-Ga-S glass.