Irradiation Effects in Ices by Energetic Ions
It has been shown that the irradiation of ices leads to “giant” erosion yields, in some specific conditions (1,2). In order to understand the physical processes involved, we have performed direct in-situ measurements of the erosion during irradiation, by means of infrared spectrometry of the ices. In this paper, we summarize the main results we obtained, during the irradiation of a number of ices (pure H2O or CH4; mixtures: H2O + CO2; H2O + NH3; CO2 + NH3) with ions in a wide range of energy (a few keV/u to a few MeV/u) and mass. We have performed experiments both with chemically reactive ions (C, N, H, H2) and unreactive ones (He, Ne, Ar, Kr). In addition to the erosion process, we discuss the synthesis of molecular species, induced by the irradiation. Furthermore, we have analyzed the ions desorbed from the targets during the irradiation, by time of flight mass spectrometry. The comparison between the yields of erosion and of ion desorption gives information on the ion/neutral ratio of the ejected material, as well as its dependence with mass and energy of the incident particles. We conclude this paper with some astrophysical implications of our results.
KeywordsIncident Particle Abundant Cluster Desorption Yield Astrophysical Implication Molecular Synthesis
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