Angular distributions of reactive scattering arising from persistent complexes with oblate symmetric top transition states

Microcanonical transition state theory, as previously applied to scattering via a prolate symmetric top transition state, is extended to predict the angular distribution of reactive scattering arising from a long-lived collision complex dissociating via a transition state which approximates to an oblate symmetric top. Sideways peaked angular distributions are described by a simple formula with parameters which depend upon the structure and energetics of the transition state. This gives a mildly peaked angular distribution for reactive scattering via H atom elimination for the F + C 2 H 4 reaction which is in excellent agreement with the experimental distribution. Isotropic scattering represents a limiting case which adjoins the range of forward and backward peaked distributions which has been described previously for reactive scattering via a prolate top transition state. Taken together the formulae for oblate and prolate tops now provide a comprehensive description of angular distributions of reactive scattering in terms of the structure and dynamics of the transition state.