Double ionization of helium in collision with 20–500-keV/amu ${\text{C}}^{q+}$ and ${\text{O}}^{q+}$ $\left(q=1–3\right)$ ions

Target ionization and projectile charge changing were investigated for 20–500 keV/u ${\text{C}}^{q+}$, ${\text{O}}^{q+}+\text{He}$ $\left(q=1–3\right)$ 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.

Figure 1

The two-dimensional coincident spectrum of 3.0 MeV ${\text{C}}^{3+}-\text{He}$.

Figure 2

Cross-section ratios $R_{21}$ in ${\text{C}}^{+}+\text{He}$ collisions.

Figure 3

Cross-section ratios $R_{21}$ in ${\text{O}}^{+}+\text{He}$ collisions.

Figure 4

Cross-section ratios $R_{21}$ in ${\text{C}}^{2+}+\text{He}$ collisions.

Figure 5

Cross-section ratios $R_{21}$ in ${\text{O}}^{2+}+\text{He}$ collisions.

Figure 6

Cross-section ratios $R_{21}$ in ${\text{C}}^{3+}+\text{He}$ collisions.

Figure 7

Cross-section ratios $R_{21}$ in ${\text{O}}^{3+}+\text{He}$ collisions.