Ammonia and water physisorption on a H-passivated Si(111) surface: a study of admolecule motions

Recent results on the stability of adsorption sites and on the equilibrium configuration of NH 3 and H 2 O molecules adsorbed on H-terminated Si(111) are used to determine the translational and orientational motions of these admolecules. The analysis of the corresponding quantum levels is a preliminary and necessary step for a further study of the dynamical processes connected to the sticking, surface diffusion and desorption of these molecules. First results allow us to discuss some aspects of the adsorption—desorption mechanisms.