Hyperthermal chemistry in the gas phase and on surfaces: theoretical studies

We review recent theoretical studies aimed at understanding gas/surface and gas-phase collisions at hyperthermal energies. The review is restricted to interactions between neutral species, and particular attention is given to the interactions of hyperthermal ground-state atomic oxygen (O(3P)) with hydrocarbons. Quantum mechanical and molecular dynamics calculations are used to simulate collisions of O(3P) with gas-phase methane, ethane, and propane molecules and with condensed-phase alkanethiolate self-assembled monolayers. The results of such studies are examined in the light of atomic-oxygen degradation of polymeric materials in low Earth orbit (LEO).