Desorption of solid hydrogen by energetic protons, deuterons, and electrons

Abstract
The yield of condensed gas released from liquid‐helium‐cooled surfaces under particle bombardment has been measured as a function of surface coverage. The yield has been found to increase at low coverage, then become roughly independent of coverage, and finally to decrease at very high coverage. The observed value of the yield has been found to exceed 104 atoms/ion and this value has been explained in terms of a thermal spike model. Where the condensed layer thickness is greater than the range of the incident ions the yield is typically 102−103 atoms/ion. This cannot be explained either by thermal spike or conventional sputtering, and it is suggested that ionization of the condensed gas leads to gas release.