Dielectronic recombination of Mg+

Cross sections for the dielectronic recombination (DER) of electrons with Mg + (3s) are calculated for electron energies just below the 3s to 3p excitation threshold. Fine structure is explicitly treated by using pair coupling to define the states Mg(3p(J i ); nl), and the autoionisation rates of these states are obtained by extrapolating electron-ion scattering calculations downward across the ionisation threshold using quantum defect theory. The physical effect of fine structure is significant; a manifold of autoionising states split by the spin-orbit interaction makes a greater contribution to the cross section than the same number of degenerate states. The present results, averaged over the experimental conditions of Belic et al. (1983), have a maximum value of 4.2*10 -18 cm 2 .