Angular distributions of reactive scattering arising from persistent complexes by transverse dissociation of symmetric-top transition states

Microcanonical transition-state theory has been employed to predict angular distributions of reactive scattering that arise from a long-lived collision complex dissociating via a transition state that approximates to a symmetric top when the direction of dissociation is perpendicular to the top axis. Bimodal peaking in the sideways direction is predicted for a prolate-symmetric-top transition state, while forward and backward peaking is predicted for an oblate-top transition state. In both cases the parameters determining the angular distributions depend upon the structure and energetics of the transition state. Sideways peaking is predicted in good agreement with reactive-scattering data for F + C2H4 at higher initial translational energy E ≳ 10 kJ mol-1 when the transition state precesses as a prolate top and H-atom displacement occurs perpendicular to the plane of the heavy atoms. The emergence of forward and backward scattering at lower initial translational energy E ≈ 5 kJ mol-1 is attributed to tran...