Theory of electron-stimulated desorption of physisorbed species through a strongly bonding excited state

A model of the electron-stimulated desorption of physisorbed species is proposed in which the excited-state surface potential is due to a chemical rather than image force acting on the adsorbed particle after the initial electron excitation is completed. The equilibrium positions of the excited- and the ground-state potentials nearly coincide and desorption is a purely quantum-mechanical effect. A one-dimensional model is systematically derived from the three-dimensional theory. The oscillatory structure of the resulting kinetic-energy distributions of the desorbing species is predicted in certain cases. It is demonstrated that, unlike in the commonly accepted Antoniewicz model, both the kinetic-energy distributions of the desorbing neutral particles and the total desorption yield calculated in the present model are consistent with the experimental data for Ar and N₂O physisorbed on Ru(001).