Electron-stimulated desorption of D₂O coadsorbed with CO₂ ice at VUV and EUV energies

The (C⁺, O⁺, CO⁺, O₂⁺, D⁺, D₃⁺) desorption yields during the (10-100 eV) electron beam irradiation of CO₂ ice and of D₂O adsorbed on CO₂ ice were measured. Measurements of pure CO₂ ice irradiated with 40-eV electrons suggest that pores in the CO₂ are responsible for trapping molecular precursors for bimolecular reactions that are responsible for O₂⁺ production. Investigations of pure CO₂ ice irradiated with a 100-eV electron reveals production of O₂⁺ by a second channel. It was found that D₂O adsorbed on solid carbon dioxide at 30 K diffuses into solid CO₂ due to exposure to the electron beam irradiation. Without radiation, D₂O stays on the top of the CO₂ ice.