Energy transfer in water cluster scattering from solid surfaces

Abstract

Classical trajectory calculations of (H2O)n (n ≤ 123)scattering from rigid model surfaces are presented. Three different intramolecular water potentials are employed together with both flat and corrugated surfaces. Clusters with an internal temperature of 180 K are scattered from the surface with incident velocities of 400–2000 m/s, and energy conversion during surface interaction is followed by probing the temperatures of various degrees of freedom. Molecular translation within the cluster couples strongly to the surface potential resulting in a compression phase of the cluster and a temperature peak 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 the stretch modes. Cluster fragmentation is very low up to 1300 m/s and thereafter increases with velocity. The energy redistribution at impact depends only weakly on cluster size and the surface potential employed. The total energy transfer efficiency is largely determined by the maximum surface potential energy during the scattering event.