STATE-RESOLVED TRANSLATIONAL ENERGY-DISTRIBUTIONS OF CL AND HCL IN THE ULTRAVIOLET PHOTODISSOCIATION OF CHLOROETHYLENES

Velocity-aligned Doppler spectroscopy was used to measure the speed di stribution functions of HCl(v '' = 0-2,J '') produced in the 193 nm ph otodissociation of vinyl chloride. A mechanism which is consistent wit h our present data as well with our earlier work is three center elimi nation of HCl followed by concerted but nonsynchronous isomerization o f the vinylidene fragment, with some of the isomerization energy conve rted to kinetic energy of the recoiling fragments. In order to explain the vibrational dependence of the translational and rotational energy distributions, the mechanism is assumed to be vibrationally adiabatic . In addition, magic angle Doppler spectroscopy was used to measure th e speed distribution functions of Cl atoms produced in the photodissoc iation of vinyl chloride and the three dichloroethylene isomers. Bimod al energy distributions were observed for both spin-orbit states, with the Cl(P-2(1/2)) fragment having more kinetic energy than Cl(P-2(3/2) ). The data are consistent with competitive reaction on two potential energy surfaces. Adiabatic correlation, with some scrambling in the as ymptotic region, provide a qualitative explanation of the spin-orbit b ranching ratios. (C) 1995 American Institute of Physics.