Time evolution of reactants, intermediates, and products in the vibrational predissociation of Br-2 center dot center dot center dot Ne: A theoretical study

A hybrid quantum/classical simulation of the vibrational predissociation of the Br-2. . . Ne cluster in the B state is carried out. The resulting life times and final rovibrational state distributions compare very well with th e experimental measurements, as well as with accurate quantum mechanical re sults. 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 vibr ational redistribution followed by evaporative cooling relative to direct v ibrational predissociation is shown to evolve from 100% of VP for the lowes t initial vibrational level v=10 to 53% for the highest one v=27. In the ca ses where IVR is important, the complexes are shown to explore the whole co nfiguration space, in contrast with the cases where dynamics are governed b y direct vibrational predissociation for which the complexes mainly evolve in the region around the T-shaped equilibrium configuration. A time-depende nt picosecond experiment is proposed to detect the IVR intermediates, based on their different structure. It consists of exciting the complex with a f irst laser and probing the intermediates with a second laser to an electron ic 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 apprecia ble population of intermediates is predicted for initial excited levels wit h v greater than or equal to 20. (C) 2000 American Institute of Physics. [S 0021-9606(00)01946-2].