The 193 nm photodissociation of 1,1- and 1,2-difluoroethylene

The photodissociation of 1,1- and 1,2-difluoroethylene (DFE) at 193 nm was studied by measuring product translational energy distributions, P(E-T), for the various product channels. The P(E-T)'s are used to obtain information on the exit barriers, product internal energy, transition states, and the stability of intermediates in many of these channels. Significant differences in the P(E-T)'s for three-centered elimination of HF to produce:C=CHF and four-centered elimination of HF to give HC=CF were observed. These were attributed to differences in the exit barriers and transition states for the two types of elimination. This is the first reported study of the three-and four-centered H-2 elimination pathways producing:C=CF2 and FC=CF, respectively. Both reactions showed the presence of a small exit barrier. This work also gives the first detailed description of the H and F atomic elimination channels. The P(E-T) for primary H atom elimination indicates a simple bond rupture mechanism; the P(E-T) for secondary H atom elimination suggests that triplet product is formed. The P(E-T)'s for F atom elimination indicate that (CH)-C-.=CHF is more stable than (CF)-C-.=CH2. Where appropriate, comparisons of the various DFE and ethylene photodissociation channels were made.