Light atom scattering from adsorbates at low coverage

A multiple scattering theory is developed for the scattering of light atoms from a disordered adsorbate on a smooth surface. Using gas phase potentials for adatom potentials, excellent agreement is found with data for He scattering from adsorbed Xe and surprisingly good agreement with the extensive data for He scattering from adsorbed CO. The attractive adatom potential must be included in the calculation if quantitative comparison with experimental data is to be made. An important contribution to the total cross section of an adatom are quantum mechanical oscillations similar to glory oscillations in gas phase scattering. The dependence of the total cross section on the incident angle is strongly influenced by the varying number of adatoms seen by the probe.