Direct ionization of helium by low and intermediate C q+ and O q+ ( q = 1–4) ions

Abstract

Cross-section ratios σ DDI/ σ DSI of direct double ionization (DDI) to direct single ionization (DSI) of C q+ – and O q+ –He ( q = 1–4) collisions in the energy range of 15–480 keV/u (0.8 a.u. ≤ v p ≤ 4.4 a.u.) are experimentally determined. For a fixed projectile charge the ratios depend strongly on the projectile energy and there is a maximum at about 100 q 1/2 keV/u. Comparison is made with other available experimental data. The present results are in agreement with the previously published data. On the whole, the ratios appear in two groups according to the different projectile ions. Combining the Bohr–Lindhard model and statistical model, a theoretical estimate is presented. The estimate shows the trend in good agreement with experimental data.