PHOTODISSOCIATION OF ACETYL-CHLORIDE - CL AND CH, QUANTUM YIELDS AND ENERGY-DISTRIBUTIONS

Jet cooled acetyl chloride is dissociated at 236 nm via excitation of the (1)[n, pi* (C=O)] transition. Chlorine atom photofragments Cl(P-2(3/2)) and Cl*(P-2(1/2)) are detected using (2+1) multiphoton ionization. The relative Cl* yield phi*=[Cl*]/([Cl]+[Cl*]) is measured to be 0.4+/-0.02, and the mean translational energy of the Cl atoms is 0.28+/-0.02 eV. Methyl fragments are also detected following primary dissociation and the internal state distributions are probed using (2+1) multiphoton ionization through the 4p(z) Rydberg state at 286 nm and the 3p(z) Rydberg state at 334 nm. The quantum yield for CH3 formation is estimated to be 28%, relative to the CH3 yield from methyl iodide photolysis. A small fraction of the available energy is channeled into methyl fragment angular momentum as the rotational state distribution extends only to N''=5. Our results indicate that CH3CO, generated as a primary photoproduct in the dissociation of acetyl chloride, subsequently decomposes to produce CH3 and CO, Energetic constraints in the mechanism of acetyl chloride dissociation are discussed.