Effect of surface roughness on the electron-stimulated desorption of D⁺ from microporous D₂O ice

The electron-stimulated desorption (ESD) of D⁺ from microporous D₂O ice films condensed on Pt(111) has been investigated. The total D⁺ yield as a function of temperature from 90-180 K depends sensitively on the film roughness, surface temperature and ice phase. In particular, we observe an irreversible increase in the cation yield as the microporous thin film is heated from 90-120 K, which we associate with a decrease in surface roughness as the micropores collapse. We present evidence which suggests that the number of surface sites available for emission, the surface roughness, and reneutralization or reactive scattering of the D⁺ desorbate play major roles in determining the ion yield. A simple model which qualitatively addresses the role of surface roughening on ESD ion yields shows good agreement with the data.