Double ionization of helium in collision with 20–500-keV/amuCq+andOq+(q=1–3)ions

Abstract

Target ionization and projectile charge changing were investigated for 20--500 keV/u ${\text{C}}^{q+}$, ${\text{O}}^{q+}+\text{He}$ $(q=1--3)$ collisions. Double- to single-ionization ratios ${R}_{21}$ of helium associated with no projectile charge change (direct ionization), single-electron capture, and single-electron loss were measured. The cross-section ratio ${R}_{21}$ depends strongly on the collision velocity $v$, the projectile charge state $q$, and the outgoing reaction channel. Meanwhile, a model extended from our previous work [J. X. Shao, X. M. Chen, and B. W. Ding, Phys. Rev. A 75, 012701 (2007)] is presented to interpret the above-mentioned dependences. Good agreement is found between the model and the experimental data.