Scattering of CO and N2 molecules by a graphite surface

Abstract

Measurements of angular distributions for the scattering of well-defined incident beams of CO and N2 molecules from a graphite surface are presented. The measurements were carried out over a range of graphite surface temperatures from 150 to 400 K and a range of incident translational energies from 275 to over 600 meV. The behavior of the widths, positions and relative intensities of the angular distributions for both CO and N2 were found to be quite similar. The experimental measurements are discussed in comparison with calculations using a classical mechanical model that describes single collisions with a surface. Based on the behavior of the angular distributions as functions of temperature and incident translational energy, and the agreement between measured data and calculations of the single-collision model, it is concluded that the scattering process is predominantly a single collision with a collective surface for which the effective mass is significantly larger than that of a single carbon atom. This conclusion is consistent with that of earlier experiments for molecular beams of O2 molecules and Xe atoms scattering from graphite. Further calculations are carried out with the theoretical molecular scattering model in order to predict translational and rotational energy transfers to and from the molecule during scattering events under similar initial conditions.