Rotational distributions of HBr in the photodissociation of vinyl bromide at 193 nm: An investigation by direct quasiclassical trajectory calculations

The three-center (3C) and four-center (4C) HBr eliminations in the photodissociation of vinyl bromide at 193 nm were investigated by direct quasiclassical trajectory (QCT) calculations using a semiempirical AM1 Hamiltonian with specific reaction parameters. The trajectories were initiated at the corresponding transition states under microcanonical conditions. The calculations show that the 4C distributions are displaced towards higher J values in comparison with the 3C distributions. The total QCT rotational distributions, i.e., those obtained by weighted sums of the 3C and 4C contributions, do not follow the bimodal pattern obtained elsewhere by time-resolved Fourier transform spectroscopy in a flow system.