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1.
The structure of oxalyl bromide (COBr)2 in the ground and four lowest excited electronic states was theoretically investigated using the CASPT2/cc-pVTZ-DK method. Structural information obtained allowed the reassignment of the and vibronic absorption spectra. Generalization of oxalyl halide structural data for the ground and excited electronic states is presented. 相似文献
2.
3.
The results of the analysis of the fluorescence excitation spectrum of trans-hexafluorobiacetyl published earlier are revised.
New values of torsion frequencies and potential barriers of internal rotation of the CF3 group in the ground and excited states of the molecule are obtained. A procedure for calculating the probabilities of torsional
vibronic transitions of molecules is described.
Translated fromZhurnal Struktumoi Khirnii, Vol. 38, No. 2, pp. 293–302, March–April, 1997. 相似文献
4.
V. A. Bataev E. K. Dolgov A. V. Abramenkov G. M. Kuramshina I. A. Godunov 《Russian Chemical Bulletin》2000,49(6):984-990
The molecular structure of 2,2-difluoroethanal (DFE) in the ground (S0) and lowest excited triplet (Ti) electronic states was investigated byab initio quantum-chemical methods. In the S0 state, the DFE molecule exists as the only stablecis conformer. The Ti↓S0 electronic excitation is accompanied by the rotation of the top and the deviation of the carbonyl fragment from planarity.
For the DFE molecule in the Ti state, six minima corresponding to three pairs of enantiomers were found on the potential energy surface. Based on this potential
energy surface, the problems on torsion and inversion nuclear motions were solved in the one- and two-dimensional approximations,
and the interaction between these motions was revealed.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 989–995, June, 2000. 相似文献
5.
V. A. Bataev M. N. Mikhailov A. V. Abramenkov V. I. Pupyshev I. A. Godunov 《Journal of Structural Chemistry》2001,42(1):57-65
This paper reports on an ab initio quantum mechanical calculation of the structure of the conformationally nonrigid chloral (CCl3CHO) molecule in the ground (S0) and lowest excited triplet (T1) states. Electronic excitation causes substantial changes in molecular geometry: the CCl3 top is rotated, and the carbonyl (CCHO) fragment becomes nonplanar. For the torsional (S0 and T1) and inversion (T1) nuclear vibrations, one- (S0 and T1) and two-dimensional (T1) vibrational problems are solved; a relationship is found between the torsional and inversion vibrations in the T1 state. The results are compared with the data of analogous calculations for the acetaldehyde molecule in the T1 state. 相似文献
6.
The structure of the conformationally flexible 2-fluoroethanal molecule (CH2FCHO, FE) in the ground (S0) and lowest excited triplet (T1) and singlet (S1) electronic states was investigated by ab initio quantum-chemical methods. The FE molecule in the S0 state was found to exist as two conformers, viz., as cis (the F—C—C—O angle is 0°) and trans (the F—C—C—O angle is 180°) conformers. On going both to the T1 and S1 states, the FE molecule undergoes substantial structural changes, in particular, the CH2F top is rotated with respect to the core and the carbonyl CCHO fragment becomes nonplanar. The potential energy surfaces for the T1 and S1 states are qualitatively similar, viz., six minima in each of the excited states of FE correspond to three pairs of mirror-symmetrical conformers. Based on the potential energy surfaces calculated for the FE molecule in the T1 and S1 states, the one-dimensional problems on the torsion and inversion nuclear motions as well as the two-dimensional torsion-inversion problems were solved. 相似文献
7.
S. K. Godunov V. T. Zhukov O. B. Feodoritova 《Computational Mathematics and Mathematical Physics》2006,46(6):971-982
An algorithm is constructed for calculating invariant subspaces of symmetric hyperbolic systems arising in electromagnetic, acoustic, and elasticity problems. Discrete approximations are calculated for subspaces that correspond to minimal eigenvalues and smooth eigenfunctions. Difficulties related to the presence of an infinite-dimensional kernel in the differential operator are successfully handled. The efficiency of the algorithm is demonstrated using acoustics equations. 相似文献
8.
The vapor-state absorption spectra have been recorded for propanal PA and 2-methylpropanal MP with path lengths up to 120 m. The initial points in the S1S0 electronic transitions have been identified together with various fundamental vibrational frequencies of the PA and MP conformers. They contain nonplanar aldehyde groups in the S1 states with inversion potential barriers of about 600 cm–1. The parameters of the internal-rotation potential functions in the S1 states have been determined, and the corresponding potential functions in the S0 states have been refined.Chemical Faculty, Lomonosov Moscow University. Translated from Zhurnal Strukturnoi Khimii, Vol. 34, No. 1, pp. 20–25, January–February, 1993. 相似文献
9.
Application of vibronic spectroscopy to the conformational analysis of molecules in the ground and excited electronic states is reviewed. The basic concepts of the method as well as its methodological and technical aspects are discussed. The abilities of vibronic spectroscopy are exemplified by the results obtained for molecules of carbonyl compounds.The review is based on a report at the Vibrational Spectroscopy Conference dedicated to the 80th birthday of B. I. Stepanov (Minsk, Belarus', October 3–5, 1993).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 783–791, May, 1994.This work was performed with the partial financial support of the Russian.Universities State Program. 相似文献
10.
UV absorption spectra of acetyl fluoride-h3 and -d3 (CH3COF and CD3COF) molecules in the region of S1S0 electronic transitions are investigated. The origins (00
0 or 140±
0) of these transitions are observed at 39912 and 39904 cm–1, respectively, and some of the fundamental frequencies of these molecules in the s0 and S1 states are determined. In particular, the systems of torsion and inversion (out-of-plane C=O vibrations) energy levels are studied. The geometric parameters of an acetyl fluoride-h3 molecule in the S1 state are estimated by the theoretical simulation of the rotational contours of the 00
0 (140±
0) band. These data are used to evaluate the potential barriers to internal rotation in the S0 and S1 states, which were found to be 360 and 560 cm–1 for acetyl fluoride-h3 and 380 and 770 cm–1 for acetyl fluoride-d3, respectively, as well as the potential barriers to inversion in the S1 states, which were found to be 2090 and 2370 cm–1 for acetyl fluoride-h3 and acetyl fluoride-d3, respectively.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1957–1964, November, 1994.In conclusion, the authors would like to acknowledge T. S. Kuznetsova for the synthesis and purification of the AF samples.The research presented here was supported in part by the International Science Foundation under grant No. MJ 1000. 相似文献