C6H5Br+•→C6H5++Br• occurs via orbiting transition state

Photodissociation of the bromobenzene molecular ion has been investigated on a nanosecond time scale by photodissociation mass-analyzed ion kinetic energy spectrometry. The rate constant and kinetic energy release distribution have been determined. The present experimental data together with the previous milli- to microsecond data have been compared with theoretical calculations. The rate-energy data available over 6 orders of magnitude in time scale could be fit with a nontotally loose transition state model (RRKM) reported by Rosenstock and co-workers. However, the model has been found to predict rate constant values larger than theoretically acceptable at high internal energy. The completely loose transition state model, namely the reaction occurring via orbiting transition state. seems to be a better description of the reaction.