[en] The expected angular distributions of ejected particles from ion-bombareded clean and reacted single-crystal surfaces are calculated using classical dynamics to model the momentum dissipation. For oxygen atoms adsorbed on a Cu(100) lattice in A-top and fourfold and twofold bridged geometries, preferred ejection angles are found for the higher-kinetic-energy particles (> 20 eV). Because of scattering mechanisms which cause atoms to move through gaps in the lattice surface, we find that the patterns for different overlayer registries are easily distinguishable