ULTRAVIOLET ELIMINATION OF H-2 FROM CHLOROETHYLENES

The elimination of H-2 in the photodissociation of mono- and di-chloroethylenes was studied with a pump-and-probe technique. A 193 nm excimer laser was used to photodissociate the parent molecules, and a tunable dye laser was used to probe the H-2 fragment by 2+1 resonance-enhanced multiphoton ionization (REMPI). The nascent rotational state distributions of H-2(X(1) Sigma(g)(+) v ''=0-4) were extracted from the REMPI spectra, and were found to have Boltzmann-type distributions. The maximum and average translational energies for some of the rovibrational levels of Hz were measured using magic angle Doppler spectroscopy. The translational energy of the fragments plus the internal energy of H-2 was found to exceed the available energy for a three-center elimination mechanism. It is concluded that a migration mechanism plays a significant role in H-2 elimination. (C) 1995 American Institute of Physics.