Model calculations of resonant vibration to vibration transition probabilities in clusters

Abstract

Results are presented for the calculated probability for resonant transfer of vibrational excitation energy in clusters of identical molecules. The calculations are performed for two-dimensional clusters in order to allow for calculations on larger clusters. Clusters of 5, 10, and 20 molecules are considered. The probability of resonant transfer is calculated by quantum mechanically propagating the wave function for the vibrational degrees of freedom of the molecules in the cluster, while the rotational and translational degrees of freedom evolve along classical trajectories. The transition probabilities are averaged over a canonical distribution of initial phase space points for the trajectories. If the probability for the transition of a vibrational quantum of energy from one molecule to some other molecule in an N molecule cluster is evaluated as N−1 independent two molecule vibrational problems, the results are found to be in excellent agreement with those obtained from the propagation of the full N molecule vibrational problem. The results also show that quantum coherence effects result in an early time nonlinear behavior in the transition probabilities that persists for several picoseconds in these systems.