ELECTRON-IMPACT IONIZATION OF THE HYDROGEN-LIKE IONS B4+, C5+, N6+ AND O7+

For the first time absolute cross sections for electron impact ionizat ion of the hydrogen-like ions B4+, C5+, N6+ and O7+ at electron energi es 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 c ross sections along the hydrogen isoelectronic sequence is discussed. A recently developed scaling technique allows us to predict all non-re lativistic cross sections along the isoelectronic sequence on an absol ute scale.