Electron-induced processes in water ice and CO2 ice are important in planetary science. We have measured desorption yields of positive ion products (C+,O+,D+,D3O+,CO+,O2+) produced as a result of exposing pure CO2 and D2O adsorbed on CO2 ices to 10–100 eV (i.e., the vacuum-ultraviolet–extreme-ultraviolet energy region) electron beams. Measurements on pure CO2 ice irradiated with 40-eV electrons suggest that pores in the CO2 ice 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 beam reveals production of O2+ by a second channel attributed to post-ion molecule collisions that are strongly influenced by low-energy electrons trapped in the ice. The most significant finding is that the D+ and D3O+ yields as a function of both dose and time indicate that the D2O adsorbed on CO2 at 30 K diffuses into the CO2 ice or desorbs into vacuum very rapidly. Both processes are a result of electron irradiation.

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