Target ionization and projectile charge changing in0.5–8−MeV/q Liq++He(q=1,2,3)collisions

Abstract

Target ionization and projectile charge changing were investigated for $0.5--8\ensuremath{-}\mathrm{MeV}/q {\mathrm{Li}}^{q+}+\mathrm{He}$ $(q=1,2,3)$ collisions. Cross sections for the single and double ionization of He associated with no projectile charge change (direct ionization), single-electron capture, and single-electron loss were measured using coincidence techniques and compared to existing experimental and theoretical results. Total cross sections for single-electron capture (for ${\mathrm{Li}}^{1,2,3+}$) and single-electron loss (for ${\mathrm{Li}}^{1,2+}$) were also obtained. For a given incoming projectile charge state the double-to-single target ionization ratios $R$ vary strongly with the outgoing reaction channel. For direct ionization, $R$ is nearly independent of the incident projectile charge state and can be described by the semi-empirical scaling rule of Knudsen et al. [J. Phys. B 17, 3545 (1984)]. However, for ionization associated with single-electron loss and single-electron capture by the projectile, $R$ depends quite strongly on the incident charge state of the projectile. These ionization ratios $R$ are interpreted in terms of theoretical formulations involving electron-nucleus interactions and electron-electron interactions.