Models for high energy ion induced desorption of molecules from surfaces

Classical trajectory calculations of the desorption of large molecules from surfaces are considered. Initial conditions correspond to differing models for the initial excitation mechanism of the molecular adsorbates. A linear chain of anharmonic oscillators is used to model the system. Results for the popcorn and thermal spike mechanism are given. In both cases the essential dynamical feature of the desorption is found to be the coupling of the expansion mode of the system to the desorption mode. Simple dynamical models also will be presented for large molecular adsorbates which include a few important degrees of freedom and an internal heat bath. Applications of these models to large scale simulations will be considered