Single and multiple electron removal processes in proton–water-molecule collisions

Abstract

Charge-state correlated cross sections for single- and multiple-electron removal processes (capture and ionization) in proton-H${}_{2}$O collisions are calculated by using the nonperturbative basis generator method adapted for ion-molecule collisions [Phys. Rev. A 80, 060702(R) (2009)]. The results are compared with experimental data for a wide range of impact energies spanning from 20 keV to several MeV. Single-electron removal probabilities in each molecular orbital are evaluated using the inclusive-probability formalism to predict the yields of charged fragments (H${}_{2}$O${}^{+}$, OH${}^{+}$, H${}^{+}$, O${}^{+}$) according to branching ratios that are valid at high impact energies. At intermediate and low energies, we calculate improved fragmentation cross sections that include the effects of multiple-electron removal processes. The resulting fragmentation yields agree with experiments at the 20$%$--30$%$ level even below 100 keV impact energy.