Photodissociation spectroscopy and dynamics of the methylthio radical (CH3S)

The photodissociation spectroscopy and dynamics of the CH3S and CD3S radica ls have been investigated using fast radical beam photofragment spectroscop y of the (A) over tilde (2)A(1) <-- (X) over tilde E-2 electronic band (T(0 )congruent to 26 400 cm(-1)) and an unstructured band near 45 600 cm(-1). A t all energies, only one major channel, CH3((X) over tilde (2)A(2)") + S(P- 3(j)), was observed. Photofragment yield spectra for the (A) over tilde (2) A(1) <-- (X) over tilde E-2 electronic band show resolved vibrational progr essions extending well beyond those seen in laser-induced fluorescence stud ies of this band. Photofragment translational energy distributions yield th e S(P-3(j)) fine-structure distribution for each vibrational level of the C H3 product. Photofragment angular distributions were found to be highly ani sotropic (beta= - 0.2 to - 1.0+/-0.1) with increasing anisotropy at higher photon energies. The results yield a refined heat of formation for CH3S (1. 346+/-0.018 eV) as well as the mechanism by which the (A) over tilde (2)A(1 ) State is predissociated. Results at 45 600 cm(-1) imply that dissociation occurs on the repulsive (B) over tilde (2)A(2) state. (C) 1999 American In stitute of Physics. [S0021-9606(99)04201-4].