NUMERICAL STUDY OF THE MULTIPLE-SCATTERING SERIES FOR GAS-SOLID DYNAMICS INCLUDING SINGLE-COLLISION THROUGH TRIPLE-COLLISION TERMS

The multiple-scattering series for the transition amplitude in gas-sur face collisions is examined using elastic atom-surface diffraction as a test bed. Performing numerical calculations for various scattering a ngles and incident energies, we assess the role of double and triple s uccessive collisions between the projectile and the surface atoms. For rigid lattices, double- and triple-collision terms are found to be si gnificant in the thermal energy regime and even in the higher-energy r egime if the surface is highly corrugated. However, at superthermal in cident energies (E greater than or similar to 0.2 eV), the single-coll ision terms give a good approximation to the overall scattering intens ities, provided that the ranges of the atom-pair potentials do not ove rlap; nevertheless, multiple, collisions are still important in elasti c scattering with large parallel momentum transfers. These results ind icate that single-collision approximations should be employed with car e for elastic diffraction.