Quasi-classical trajectory study of H2 elimination in the photodissociation of difluoroethylenes at 193 nm

Abstract

Direct quasi-classical trajectories were carried out to calculate translational energy distributions, P(ET), for the elimination of molecular hydrogen from 1,1- and 1,2-difluoroethylene (DFE) at 193 nm. A reasonably good agreement is found between the calculated and the experimental distributions. The calculations corroborate that the elimination from 1,1-DFE takes place through the expected (direct) three-center mechanism (leading to :C=CF2 and H2), which essentially has no exit barrier. For the photodissociation of 1,2-DFE, the results strongly support that the most important pathway for H2 elimination involves a previous isomerization to 1,1-DFE, which then dissociates via the three-center mechanism. A minor contribution from a pathway having a large exit channel barrier is responsible for the long tail decay of the P(ET) in comparison to that of 1,1-DFE.