Multiple ionization effects on the yields of HO2/O2− and H2O2 produced in the radiolysis of liquid water with high-LET 12C6+ ions: a Monte-Carlo simulation study

Monte-Carlo simulations are used to investigate the effects of multiple ionization on the formation of HO2/O2− and H2O2 in the radiolysis of water by 12C6+ ions up to ∼430 keV/μm, at neutral pH and 25 °C. Taking into account the double and triple ionizations of water molecules, the primary yields GHO2/O2− and GH2O2 are calculated as a function of linear energy transfer (LET). Our results quantitatively reproduce the large increase observed in GHO2/O2− at high LET. They also simultaneously predict a slight maximum in GH2O2 at ∼180–200 keV/μm, in excellent agreement with experiment. Under the conditions of this study, triple ionization is found to contribute only negligibly to GHO2/O2−.