Scattering from disordered surfaces in the sudden approximation

The angular intensity distribution of atomic beams scattered from partially disordered solid surfaces is investigated. Quantitative relations are established between correlation functions that describe the structural disorder, and several features of the scattered intensity distribution. To simplify the collision dynamics, the study is carried out in the framework of the sudden approximation, which assumes that momentum changes perpendicular to the surface are large compared with momentum transfer due to surface corrugation. Simple relations are obtained between the structural correlation functions and the scattering at near-specular angles, at extreme off-specular angles, and for directions close to that at which the surface scattering rainbow appears for the corresponding ordered lattice system. Detailed expressions for the case of step disorder are presented. The results suggest that molecular beam scattering should be a powerful probe of structural properties of disordered surfaces.