Electron impact ionization of complex ions

Abstract

The simple procedure suggested by Burgess et al. to allow for inner-shell excitation and auto-ionization has been used with an empirical formula of similar form to that of Lotz and compared with a wide range of crossed-beam experimental data for ions of charge z ≽ 2. The resulting simple general formula for the total ionization cross-section, and the corresponding rate coefficient, represents the experimental data to within ±23 per cent rms deviation. The formula is consistent with the earlier formulae of Seaton (valid only near threshold) and of Lotz, but gives a significantly smaller rms deviation through the consistent inclusion of auto-ionization effects. For simple ions, comparisons with much more elaborate quantal calculations are satisfactory. Comparisons are also made with the simplified ECIP formula. For more complex ions, any accurate quantal calculation would require consideration of the effects of strong coupling between final states. Some allowance for these effects is included in our procedure, and agreement with experiments for these complex ions is reasonably good.