Electron Capture and Loss by Ions in Gases

Capture and loss cross sections for ions of intermediate atomic number ($Z_1=8\mathrm{} \mathrm{to} 18$) passing through low-pressure gases have been calculated. A modified form of Bell's model was used, leading to lower capture cross sections than the original model. The resulting equilibrium charge distributions obtained compare favorably with the experimental results of Hubbard and Lauer. The individual cross sections were obtained from the observed dependence of the charge distribution on the stripper thickness; these results agree reasonably well with the predictions of the calculations. Capture and loss of two electrons in a single collision may be significant, but the effect on the charge distributions should not be too great.