PHOTODISSOCIATION OF HF IN ARNHF (N=1-14,54) VAN-DER-WAALS CLUSTERS - EFFECTS OF THE SOLVENT CLUSTER-SIZE ON THE SOLUTE FRAGMENTATION DYNAMICS

A comprehensive study of the photodissociation of HF in Ar,HF van der Waals clusters, with n=1-14,54, for an ultrashort delta(t)-pulse excitation, is presented. The emphasis is on the dependence of the photodissociation dynamics of the HF solute molecule on the size and geometry of the Ar-n solvent cluster. This cluster size range encompasses formation and closing of the first solvation shell, which occurs for n=12, the addition of the complete second solvent layer (n=54), as well as the change of the HF location in the cluster, from a surface site for n less than or equal to 8 to the interior of a cage for n greater than or equal to 9 clusters. Evolution of the fragmentation dynamics is revealed by following how the H-atom kinetic energy and angular distributions, the survival probability, and cluster fragmentation patterns change as a function of the cluster size and structure. Classical trajectories are used to simulate the photodissociation dynamics. The probability distributions of the initial coordinates and momenta of the H and F atom are defined by accurate quantum five-dimensional eigenstates of the coupled, very anharmonic large amplitude intermolecular vibrations of HF in the cluster. All aspects of the dissociation process studied here are found to exhibit a strong dependence on the size and geometry of the ArnHF clusters. (C) 1995 American Institute of Physics.