Carbon chemistry due to combined H+ and O+ irradiation

An investigation of carbon chemistry due to simultaneous H+ and O+ impact of pyrolytic graphite is presented. As an introduction, an overview is given of previous results related to the chemical erosion processes of graphite due to single-species impact by hydrogen and oxygen. Some limited previous synergistic results of various multispecies impact studies of graphite are also presented. In the present investigation, pyrolytic graphite (Union Carbide HPG99) was exposed to 5 keV O+ and 1 keV H+, resulting in a 10-20% reduction of CO and CO2 erosion yields (in comparison with the O+-only case) for flux ratios of phi(O+)/phi(H+)similar to 6-27%. Maximum CO and CO2 reduction was observed at similar to 800 K graphite temperature. In addition, water production was observed with a maximum of similar to 0.15 H2O/O+ at similar to 800 K. Only a small reduction (similar to 5-10%) in the methane yield (CH4/H+) was seen. (C) 1997 Elsevier Science B.V.