A REINVESTIGATION OF THE NEAR-ULTRAVIOLET PHOTODISSOCIATION DYNAMICS OF THE METHYL RADICAL

The translational energy spectrum of H Rydberg atoms resulting from th e photolysis of the methyl radical (CH3) at 216.3 nm has been recorded . The use of pulsed supersonic jet flash pyrolysis of azomethane (CH3N 2CH3) as a clean source of methyl radicals has allowed a clear analysi s of the data, eliminating possible interference from other molecular species. The measured times-of-flight of the resulting H atoms indicat e that the partner CH2 fragments resulting from predissociation of CH3 (B) radicals are formed in their low-lying a excited state, as predic ted by theory. An earlier contradictory report of this dissociation pr ocess, using methanethiol (CH3SH) as a photolytic precursor to generat e methyl radicals, has been reinterpreted in terms of secondary dissoc iation of ground-state thiomethoxy radicals (CH3S) yielding electronic ally excited thioformaldehyde CH2S(A1A2) + H(2S).