The PEMET model of collisional energy transfer in unimolecular reactions - Comparison with molecular dynamics simulation

The semi-empirical Partially Ergodic Multiple Encounter Theory (PEMET) of collisional energy transfer has recently been proposed as a means to resolve the great Variation in transfer efficiency observed experimentally and by simulation. Here the PEMET model is tested against classical trajectory data for simple representations of the collisions of the following reactant-medium molecular pairs: Br-2 + Ar, Br-2 + Br-2, Br-2 + [Br-3] and CH3NC + Ar where [Br-3] is a simple cluster model. The intermolecular potentials are constructed from pairwise Lennard-Jones interactions between the atoms and the interaction strength is varied from the physically plausible value reflecting weak van der Waals interaction to chemical bonding strength. The simulation data show a pronounced increase in energy transfer efficiency with interaction strength which is reproduced, with some variation in accuracy, by the PEMET model. (C) 1997 Elsevier Science B.V.