Electron-impact ionization of Fe5+ ions

Employing the dynamic crossed-beams technique, absolute cross sections for single, double, and triple ionization of Fe5+ ions by electron impact have been measured from the threshold up to 1 keV, partly up to 5 keV. The data for single ionization are in very good agreement with configuration-average distorted-wave (CADW) calculations if excitation-autoionization processes are taken into account. The results for double and triple ionization are in poor agreement with semiempirical predictor formulae. Using a high resolut ion energy-scan technique, wt: have studied narrow resonances in the double ionization cross section in the energy range from 560-940 eV. Besides cont ributions from excitation-double-autoionization processes, a remarkable num ber of structures arising from resonant-excitation-triple-autoionization pr ocesses could be observed. (C) 1999 Elsevier Science B.V.