Time evolution of reactants, intermediates, and products in the vibrational predissociation of Br2⋯Ne: A theoretical study

Abstract

A hybrid quantum/classical simulation of the vibrational predissociation of the Br2⋯Ne cluster in the B state is carried out. The resulting lifetimes and final rovibrational state distributions compare very well with the experimental measurements, as well as with accurate quantum mechanical results. The time-evolution of the reactants, products, and intermediates is analyzed by a kinetic mechanism, comporting three elementary steps: direct vibrational predissociation (VP), intramolecular vibrational redistribution (IVR), and evaporative cooling (EC). The importance of intramolecular vibrational redistribution followed by evaporative cooling relative to direct vibrational predissociation is shown to evolve from 100% of VP for the lowest initial vibrational level v=10 to 53% for the highest one v=27. In the cases where IVR is important, the complexes are shown to explore the whole configuration space, in contrast with the cases where dynamics are governed by direct vibrational predissociation for which the complexes mainly evolve in the region around the T-shaped equilibrium configuration. A time-dependent picosecond experiment is proposed to detect the IVR intermediates, based on their different structure. It consists of exciting the complex with a first laser and probing the intermediates with a second laser to an electronic state with a minimum in the collinear configuration where the initially excited state wave function has no weight. The ground state of the positive ion is proposed as the final state, so that ions are detected. An appreciable population of intermediates is predicted for initial excited levels with v⩾20.