Production of Volatile CO and CO2 from Oxidized Polyethylene and Graphite Surfaces by Hyperthermal Atom–Surface Collisions

Abstract

Molecular beam-surface scattering experiments have been used to investigate the mechanisms of the enhancement in material removal rate (identified by the ejection of CO and CO₂) when continuously oxidized carbon or hydrocarbon surfaces are bombarded with inert particles (e.g. Ar atoms) possessing kinetic energies in the range 8–22 eV. Collisional enhancement in the material removal rate was observed to increase dramatically above an apparent threshold of ∼8eV. Although the details of the collisional mechanisms must involve complex sputtering processes, the dynamical behaviour of the ejected CO and CO₂ may be described in terms of a simple kinematic picture in which an incident fast atom collides with a localized region of the surface that has an effective mass. Collisional, or sputtering, processes such as those identified in this study may be important in the erosion of materials in the low Earth orbital environment, as a result of highly energetic collisions of ambient N₂ with oxidized surfaces, and also in ground-based test facilities that subject oxidized surfaces to bombardment by O₂ molecules with very high translational energies.