Electron-impact excitation of the ground state into the n ≤ 3 states of He+ between the n = 2 and n = 4 thresholds

The two-dimensional R-matrix propagator is used to calculate total cross sections and resonance parameters for electron-impact excitation of the He+ ground state into the ≤ 3 states at collision energies up to the n = 4 threshold. For the 1s-2s transition, the results are in excellent agreement with those of an algebraic variational method. Between the n = 2 threshold and the first resonances, the shape of the cross section differs from that obtained from a convergent close-coupling calculation, but is similar to that found by other methods. The long-standing discrepancy with the experimental cross sections remains. (author)