Mechanisms of O-2 sputtering from water ice by keV ions

[摘要] We have conducted experiments on the sputtering of water ice by 100 keV Ar+ between 20 and 150 K. Our findings indicate that the temperature dependence of the total sputtering yield is heavily influenced by the thermal and irradiation history of the ice, showing a complex dependence on irradiation fluence that is correlated to the ejection of O-2 molecules. The results suggest that O-2 produced by the ions inside the ice diffuses to the surface where it is trapped and then ejected via sputtering or thermal desorption. A high concentration of O-2 can trap in a subsurface layer during bombardment at 130 K, which we relate to the formation of hydrogen and its escape from that region. A simple model allows us to determine the depth profile of the absolute concentration of O-2 trapped in the ice.

[发布日期] 2005-12-01

[关键词] OUTER SOLAR-SYSTEM;CONDENSED GASES;H2O ICE;EROSION;OXYGEN;SATELLITES;DEPENDENCE;ENERGY;FILMS;YIELD