Electron impact ionization of positive ions with configurations 1s²2s²2pq

Cross sections for ionization of positive ions with configuration 1s22s22pq by electron impact are calculated in the no-exchange Coulomb-Born approximation, contributions from ejection of both 2s and 2p electrons being included. Reduced cross sections for one and twice ionized systems, and for the limiting case of infinite nuclear charge are evaluated, enabling cross sections for other systems to be obtained by interpolation. Comparison with experiment is made where possible, and agreement is good in all cases at high incident energies. In some cases there is evidence that the effects of autoionization, not included in this work could be important at low energies.