Angular and velocity distributions in molecular beam scattering at solid surfaces

The application of detailed balancing to gas-surface interactions is discussed. A consequent application of this principle shows for example that the molecules desorbing at equilibrium from a surface have in general neither a cosine distribution of the flux nor a Maxwellian distribution of the velocities corresponding to the equilibrium temperature. Experiments performed in conditions considered to be of quasi-equilibrium have confirmed the existence of important deviations from the 'classical' distributions in the case of systems involving at least partially an activated adsorption. The study of these deviations and the efficient use of the detailed balancing may provide a supplementary means for the understanding of the gas-surface interactions. (Auth.)