Ionization of rare-gas targets by collisions of fast highly charged projectiles

We have determined the net ionization cross section for total slow-ion or slow-electron charge production in rare-gas targets by passage of a fast projectile both experimentally and theoretically. We have experimentally studied ionization in these targets by C, Fe, Nb, and Pb projectiles with energies ranging from 310 keV/amu to 4.75 MeV/amu and for charge states in the range of + 4 to + 54. Theoretical calculations employing the classical-trajectory Monte Carlo method are used to calculate ionization cross sections in the rare gases for projectiles at collision energies of 1-5 MeV/amu with charge states + 5 to + 80. Experiment and theory generally agree within a factor of 2 over this wide range of conditions. For a given rare-gas target, the cross sections for net ionization reduce to a common curve when plotted as cross section divided by charge state versus energy per nucleon divided by charge state.