For the first time absolute cross sections for electron impact ionization of the hydrogen-like ions B 4+ , C 5+ , N 6+ and O 7+ at electron energies from below threshold up to about 6 keV have been measured using the crossed-beams technique. All measured cross sections are in very good agreement with available distorted-wave exchange calculations and the semiempirical Lotz formula. The behaviour of the classically scaled cross sections along the hydrogen isoelectronic sequence is discussed. A recently developed scaling technique allows us to predict all non-relativistic cross sections along the isoelectronic sequence on an absolute scale.

Employing the animated crossed-beams technique, absolute cross sections for electron impact single ionization of the iron isonuclear sequence are measured for charge states q = 1-6 for electron energies from threshold up to 1 keV, as well as for the intermediate charge states q = 9,10 up to an electron energy of 5 keV. The cross sections observed for Feq+ ions in charge states q = 1 - 4, 9 and 10 show a significant ionization signal below the respective ground state threshold resulting from ions in excited, long-lived metastable states in the parent ion beam. In the case of Fe5+ and Fe6+ no metastable components are found. The experimental results are in good agreement with the theoretical predictions if excitation-autoionization processes are taken into account. Our measured cross sections are also in good agreement with experimental results of other groups.

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Using the crossed-beams technique, cross sections for electron impact double ionization of Feq+ ions in charge states q = 1 - 6 (except 2) are measured in the energy range from the respective ionization thresholds up to 1 keV, partly up to 5 keV. The data for Fe4+, Fe5+ and Fe6+ show significant contributions from inner-shell processes. Using a high-resolution energy-scan technique, we study narrow resonances in the cross sections for Fe4+ and Fe5+. Besides contributions from excitation-autoionization processes, a remarkable number of structures arising from resonant-excitation triple-autoionization processes are observed. The results are compared with the scaling laws of Fisher et al and the semiempirical formula published by Shevelko and Tawara, respectively.

The electron-impact single ionization of low-charged Ti ions was studied both experimentally and theoretically. Absolute cross sections for Ti q+ ions in charge states q = 1 to 6 except 3 were measured using a crossed-beams technique as well as calculated with the configuration-average distorted-wave method, including both direct ionization and excitationautoionization contributions. For charge states q = 4, 5 and 6, the measurements are in good agreement with the calculations considering that large components of the incident ion beam were in metastable configurations. The cross sections for single ionization of Ti 5+ and Ti 6+ were determined in part with a high-resolution energy-scan method. Besides contributions of excitation-autoionization mechanisms, a remarkable number of structures arising from resonantexcitation double-autoionization (REDA) processes could be observed.