Broadening of the Ca+and Mg+resonance lines by collisions with helium

Model potential curves for low-lying Sigma and II states of the Ca + -He and Mg + -He systems were calculated and used to obtain fully quantal broadening and shift parameters for the Ca + 4P 1/2,3/2 to 4S and Mg + 3P 1/2,3/2 to 3S spectral lines for a range of temperatures 400-3000 K. Comparison with experiment shows satisfactory agreement for the Ca + lines but a 33% discrepancy for the only Mg + measurement, that for the k line at 556 K. Possible experimental origins for this discrepancy are discussed. Simple semiclassical dynamics is shown to be satisfactory for the high temperature Mg + and Ca + widths. Rates for fine-structure changing collisions were evaluated over the same temperature range.