INVESTIGATING CONFORMATION DEPENDENCE AND NONADIABATIC EFFECTS IN THEPHOTODISSOCIATION OF ALLYL CHLORIDE AT 193 NM

The experiments presented here investigate the competing photodissocia tion pathways for allyl chloride upon excitation of the nominally pi p i(C double bond C) transition at 193 nm. The measured photofragment v elocity distributions evidence C-Cl bond fission and HCl elimination. The recoil kinetic energy distribution for the HCl products is bimodal , indicating two primary processes for HCl elimination. The experiment al measurements show C-CI bond fission dominates, giving an absolute b ranching ratio of HCl:C-Cl=0.12+/-0.03 when the parent molecule is exp anded through a nozzle at 200 degrees C. The branching ratio depends o n the nozzle temperature; at 475 degrees C, the absolute branching rat io measured is HCl:C-Cl=0.24+/-0.03. We analyze the experimental resul ts along with supporting ab initio calculations and earlier photodisso ciation studies of vinyl chloride in order to examine the potential in fluence of nonadiabaticity along the C-Cl fission reaction coordinate and its dependence on molecular conformation. (C) 1996 American Instit ute of Physics.