Merging beams study of ionization of positive ions by electrons

The technique of beam superposition is employed in the experimental study of ionization of He+, N+ and 0+ by electrons. The electron energy range extends up to 300 eV. The primary and product ions are mass selected. Relative cross-sections for ionization are obtained as a function of the laboratory energy of the electrons. The experimental data for He+ and N+ are quite consistent with published values of the absolute cross-sections for these systems. By using Thomson’s classical scaling rule for isoelectronic systems, the cross-sections for ionization of O+ are calculated from those for ionization of atomic nitrogen. These values, when normalized to the relative ionization efficiency curve obtained experimentally here, show close overlap over the entire energy range.