Production of volatile CO and CO2 from oxidized polyethylene and graphite surfaces by hyperthermal atom-surface collisions

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 hydrocarbo n surfaces are bombarded with inert particles (e.g. Ar atoms) possessing ki netic energies in the range 8-22 eV Collisional enhancement in the material removal rate was observed to increase dramatically above an apparent thres hold of similar to8 eV. 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 surf ace that has an effective mass. Collisional, or sputtering, processes such as those identified in this study may be important in the erosion of materi als in the low Earth orbital environment, as a result of highly energetic c ollisions of ambient N-2 with oxidized surfaces, and also in ground-based t est facilities that subject oxidized surfaces to bombardment by O-2 molecul es with very high translational energies.