Classical stochastic diffusion theory for desorption from solid surfaces

We present a theory of desorption of atoms and molecules from solid surfaces based on a classical stochastic diffusion formulation. We obtain a simple rate expression which has the form R = ( Ω_o 2πf(T) exp( -D_e K_T), where T is the temperature, k is Boltzmann's constant, the bond enthalpy, and Ω_o is the surface-adsorbate vibrational frequency. For atoms √(T) = 1, while for molecules f(T) depends on the parameters for the frustrated rotations at the surface. Application of this theory is reported for the desorption of atoms and molecules. We find that molecules lead to a greatly increased (factor of 100) Arrhenius preexponential factor in excellent agreement with experiment.