Theoretical determination of the effective velocity parameter in atomic and molecular scattering from surfaces

A useful theoretical expression for interpreting and analyzing observed scattering intensity spectra for atomic and molecular collisions with surfaces is the differential reflection coefficient for a smooth, vibrating surface. This differential reflection coefficient depends on a parameter, usually expressed in dimensions of velocity, that arises due to correlated motions of neighboring regions of the surface and can be evaluated if the polarization vectors of the phonons near the surface are known. In this paper experimental conditions are suggested under which this velocity parameter may be more readily evaluated than it has been in the past.