A theoretical study of hole induced desorption

A two-dimensional quantum mechanical model describing hole induced desorption is developed and discussed. The model is used for a detailed study of hole induced molecular oxygen desorption and dissociation dynamics on a silver surface. The O-2-substrate interaction is described by four diabatic semiempirical potential energy surfaces. These potentials describe physisorption of O-2 on the substrate together with two molecular ion states (superoxide and peroxide) and a dissociative adsorption state. The model is used to correlate desorption and dissociation yields with various parameters of the system such as: excitation scheme, substrate work function (phi(m)) and isotope used (M-ad). In all cases examined, both desorption and dissociation channels were found to be active. It is demonstrated that experimental measurements of the branching ratio between these two channels and the variation of this ratio as a function of phi(m) and M-ad allows determination of the excitation route induced by the hole. (C) 1999 American Institute of Physics.