Sputtering of condensed gases by proton bombardment

The desorption of heavy gases such as Ar, N2 and CO by 5 keV protons was studied. It is a much less probable process than the desorption of the light gases such as hydrogen and helium. This is in general agreement with the very large difference in their heats of sublimation. From the present results helium appears to behave in a similar way to hydrogen with yields of approximately 104 atoms/ion and this can be explained qualitatively on the basis of the thermal spike mechanism previously developed for hydrogen. However, a detailed explanation is not yet possible because in the present experiments the helium is only adsorbed rather than condensed, and its thickness has not been well defined. (6 figures) (U.S.)