Transition-state switchings for single potential well ionic dissociations

Microcanonical variational transition state theory calculations were applied to the reaction C6HsBr'' C6H5+ + Br' in bromobenzene. Calculations were compared with experimental results for C6HS+ time-resolved photoionization efficiency curves and available k ( E ) data for this system. Calculations demonstrate, in agreement with previous results for CHI'', that multiple transition states are possible for single-well potintials of ionic systems. However, comparison with experiments indicates the dominance of the orbiting transition state over a wide energy range above threshold. Further extension of k ( E ) measurements to higher energies is recommended, in order to be able to confidently rule out transition-state switching to a tight transition state as E increases.