Classical Stochastic Diffusion Theory for Desorption of Atoms and Molecules from Solid Surfaces

A theory of desorption of atoms and molecules from solid surfaces based on a classical stochastic diffusion formulation is presented. A simple rate expression is obtained which has the form R=(Ω₀2π)f(T)exp(-DₑkT), where Ω₀ is the surface-adsorbate vibrational frequency, $f(T)=1$ for atoms, and for molecules $f(T)$ depends on the parameters for the frustrated rotations at the surface. This theory has been applied to the desorption of both atoms and molecules and excellent agreement with experiment is obtained.