ENERGY-TRANSFER IN WATER CLUSTER SCATTERING FROM SOLID-SURFACES

Classical trajectory calculations of (H2O)(n) (n less than or equal to 123) scattering from rigid model surfaces are presented. Three differ ent intramolecular water potentials are employed together with both fl at and corrugated surfaces. Clusters with an internal temperature of 1 80 K are scattered from the surface with incident velocities of 400-20 00 m/s, and energy conversion during surface interaction is followed b y probing the temperatures of various degrees of freedom. Molecular tr anslation within the cluster couples strongly to the surface potential resulting in a compression phase of the cluster and a temperature pea k at impact. Energy then dissipates to molecular rotation and further on to intramolecular vibration in the bending mode. The choice of the intramolecular potential has a strong effect only on the coupling to t he stretch modes. Cluster fragmentation is very low up to 1300 m/s and thereafter increases with velocity. The energy redistribution at impa ct depends only weakly on cluster size and the surface potential emplo yed. The total energy transfer efficiency is largely determined by the maximum surface potential energy during the scattering event.