Radiation chemistry of H2O + O2 ices

The chemistry and spectroscopy of proton-irradiated H2O + O2 ices have been investigated in relation to the production of oxidants in icy satellite surfaces. Hydrogen peroxide (H2O2), ozone (O3), and the hydroperoxy (HO2) and hydrogen trioxide (HO3) radicals have all been observed, and their temperature and dose dependent production trends have been measured. We find that O2 aggregates form during the growth of H2O + O2 ice films, and the presence of these aggregates greatly affects the HO2 and H2O2 yields. In addition, we have found that the position of the spectral maximum of the ν 3 vibration of O3 shifts with ice composition, giving an indication of the degree of dispersion of O3 molecules within the ice. We discuss the relevance of these measurements to icy satellite surfaces.