Numerical study of the multiple-scattering series for gas-solid dynamics including single- through triple-collision terms

The multiple-scattering series for the transition amplitude in gas-surface collisions is examined using elastic atom-surface diffraction as a test bed. Performing numerical calculations for various scattering angles and incident energies, we assess the role of double and triple successive collisions between the projectile and the surface atoms. For rigid lattices, double- and triple-collision terms are found to be significant in the thermal energy regime and even in the higher-energy regime if the surface is highly corrugated. However, at superthermal incident energies (E0.2 eV), the single-collision terms give a good approximation to the overall scattering intensities, provided that the ranges of the atom-pair potentials do not overlap; nevertheless, multiple collisions are still important in elastic scattering with large parallel momentum transfers. These results indicate that single-collision approximations should be employed with care for elastic diffraction.