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

N. Stolterfoht
( Physics Department, University of Florida, Gainesville, FL 32611)

R. Hellhammer, P. Sobocinski
( Hahn-Meitner-Institut, 14109 Berlin, Germany)

R. Cabrera-Trujillo, Y. Ohrn, E. Deumens, J. Sabin
( Physics Department, University of Florida, Gainesville, FL 32611)

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.

This work was supported by the Chemical Sciences, Geosciences and Biosciences Division,
Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy.

Submitted to DAMOP, May 2006 in Knoxville, TN.