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An analysis of the methyl rotation and aldehyde wagging dynamics in the S0 (X̃ 1A′) and T1 (ã3A″) states of thioacetaldehyde from pyrolysis jet spectra

AuthorsMoule, D. C.; Bascal, H. A.; Smeyers, Y. G.; Clouthier, D. J.; Karolczak, J.; Niño, A.
Issue Date30-Aug-1992
PublisherAmerican Institute of Physics
CitationJournal of Chemical Physics 97: 3964-3972 (1992)
AbstractJet-cooled, laser induced phosphorescence (LIP) excitation spectra of thioacetaldehyde (CH3CHS, CH3CDS, CD3CHS, and CD3CDS) have been observed in the 15 800-17 300 cm-1 region in a continuous pyrolysis jet. The responsible electronic transition, T1 ← S0, ã3A″ ← X̃ 1A′, results from an n → π* electron promotion and gives rise to a pattern of vibronic bands that can be attributed to activity of the methyl torsion and the aldehyde hydrogen out-of-plane wagging modes. Potential and kinetic energy surfaces were mapped out for the aldehyde wagging (α) and the torsional (Θ) internal coordinates by using 6-31G* Hartree-Fock calculations in which the structural parameters were fully relaxed. The potential and kinetic energy data points were fitted to double Fourier expansions in α and Θ and were incorporated into a two-dimensional Hamiltonian operator. The spectrum was simulated from the transition energies and the Franck-Condon factors and was compared to the observed jet cooled LIP spectra. It was concluded that while the RHF procedure gives a good description to the ground state dynamics, the triplet state surface generated by the UHF method is too bumpy and undulating. © 1992 American Institute of Physics.
Description9 pags., 7 figs., 5 tabs.
Publisher version (URL)http://dx.doi.org/10.1063/1.462935
Identifiersdoi: 10.1063/1.462935
issn: 0021-9606
Appears in Collections:(CFMAC-IEM) Artículos
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