Calculations of Ar scattering from graphite

Two recent experiments on the scattering of hyperthermal Ar atoms from clean and ordered graphite have been carried out in the classical regime, which is characterized by excitations of large numbers of phonons. The measured data, which consist primarily of angular distribution spectra, are shown here to be well explained by straight-forward classical scattering theory. The calculations confirm that the Ar-graphite scattering at energies of up to 14 eV is a single-hit collision process involving a large number of carbon atoms in the outermost graphene layers. This number is estimated here to be close to 9 carbon atoms. All of the measured angular distributions down to energies of 0.3 eV are supraspecular, but the present calculations predict that the angular distributions will become subspecular at lower energies. Calculations are also presented predicting the expected results of energy-resolved measurements under similar initial conditions.