Time-independent and time-dependent dose-coupling methods for the electron-impact ionization of Mg+, Al2+ and Si3+

The electron-impact ionization cross sections of Mg+, Al2+ and Si3+ are calculated using both time-independent and time-dependent close-coupling methods. The time-independent methods are R-matrix and convergent close-coupling solutions based on a total wavefunction constructed using antisymmetrized products of Laguerre pseudo-orbitals and physical bound orbitals. The time-dependent method is based on the propagation of wavepackets constructed using excited-state orbitals calculated in a core pseudo-potential. The results of all three methods are in good agreement for Mg+; there is also good agreement between the R-matrix and time-dependent methods for Al2+ and Si3+, and all three methods yield ionization cross sections that lie substantially above the experimental crossed-beams measurements of Crandall et al. There is better accord with the crossed-beams measurements of Peart et al for Mg+, but the theoretical results still lie 10% higher at 50 eV. Some disagreement is noted, for both Al2+ and Si3+, between the convergent close-coupling results and the R-matrix and time-dependent results.