Target ionization and projectile charge changing in 0.5–8-MeV/q Li^q++He (q=1,2,3) collisions

Target ionization and projectile charge changing were investigated for 0.5–8-MeV/q Li^q++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 Li^1,2,3+) and single-electron loss (for 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.