title: Photodissociation of gaseous CH3COSH at 248 nm by time-resolved Fourier-transform infrared emission spectroscopy: observation of three dissociation channels.
abstract: Upon one-photon excitation at 248 nm, gaseous CH(3)C(O)SH is dissociated following three pathways with the products of (1) OCS + CH(4), (2) CH(3)SH + CO, and (3) CH(2)CO + H(2)S that are detected using time-resolved Fourier-transform infrared emission spectroscopy. The excited state (1)(n(O), π*(CO)) has a radiative lifetime of 249 ± 11 ns long enough to allow for Ar collisions that induce internal conversion and enhance the fragment yields. The rate constant of collision-induced internal conversion is estimated to be 1.1 × 10(-10) cm(3) molecule(-1) s(-1). Among the primary dissociation products, a fraction of the CH(2)CO moiety may undergo further decomposition to CH(2) + CO, of which CH(2) is confirmed by reaction with O(2) producing CO(2), CO, OH, and H(2)CO. Such a secondary decomposition was not observed previously in the Ar matrix-isolated experiments. The high-resolution spectra of CO are analyzed to determine the ro-vibrational energy deposition of 8.7 ± 0.7 kcal/mol, while the remaining primary products with smaller rotational constants are recognized but cannot be spectrally resolved. The CO fragment detected is mainly ascribed to the primary production. A prior distribution method is applied to predict the vibrational distribution of CO that is consistent with the experimental findings.
authors.affiliation: Department of Chemistry, National Taiwan University, Taipei 106, Taiwan.
authors.forename: En-Lan
authors.initials: EL
authors.lastname: Hu
authors.forename: Po-Yu
authors.initials: PY
authors.lastname: Tsai
authors.forename: He
authors.initials: H
authors.lastname: Fan
authors.forename: King-Chuen
authors.initials: KC
authors.lastname: Lin