Fragmentation of H$_{2}$O by 1 -- 5 keV He$^{2+}$ ions: Experiment and Theory

Fragmentation of H$_{2}$O molecules induced by $^{3}$He$^{2+}$ impact was investigated experimentally as a function of the energy in the range from 1-5 keV. Collisions at large impact parameters are found to produce fragment protons with energies centered around peaks at 6 eV and 15 eV. The H$^{+}$ fragments were detected in the angular range from 25\r{ } to 135\r{ } with respect to the incident beam direction. Absolute fragmentation cross sections d$\sigma $/d$\Omega $, differential in the emission angle are found to be anisotropic, with protons preferentially emitted at angles near 90\r{ }. In addition to the experiments, we performed quantum-mechanical calculations to understand the fragmentation mechanisms producing protons at preferred energies and angles. The theoretical results are obtained using the Electron-Nuclear Dynamics formalism (END), which solves the time-dependent Schr\"{o}dinger equation.