Excitation of Be+ and Mg+ in collisions with He and Ne: impact parameter theory for quasi-one-electron systems

Cross sections and polarization of emission have been calculated for the excitation of ground state Be+ and Mg+ ions in collision with He and Ne atom targets in the energy range Esub(CM) = 1-100 keV. Each ion-atom pair has been treated as a quasi-one-electron system, the interaction of the valence electron of the ion with the closed-shell ion core and with the rare gas atom being represented by semi-empirical model potentials. Close-coupled solutions to the impact parameter equations have been obtained assuming a rectilinear trajectory for the relative nuclear motion and using a one-center (rotating atomic orbitals) expansion of the electronic state. The calculations for Be+ excitation are based upon the 3 states of the ion valence shell, 2s, 2p0 and 2p1, and those for Mg+ excitation upon the 6 states of the ion valence shell, 3s, 3p0, 3p1, 3d0, 3d1, 3d2, and the energetically similar 4s state. Characteristic features of the predicted excitation cross sections and the polarization of emission are in agreement with the experimental results of Andersen et al. (Auth.)