Dielectronic-recombination rate coefficients for the lithium isoelectronic sequence

The dielectronic recombination (DR) rate coefficients are calculated in the nonoverlapping resonance approximation for the target ions O/sup 5 +/, Ar/sup 15 +/, Fe/sup 23 +/, and Mo/sup 39 +/ at several electron temperatures for the initial state 1s/sup 2/2s. The autoionizing and radiative transition probabilities are computed with single-configuration, nonrelativistic Hartree-Fock wave functions and LS coupling. All possible Rydberg autoionizing states and their cascades are included. The relative contributions to the total DR rate of the 1s, 2s(..delta..nnot =0), and 2s(..delta..n = 0;2s..-->..2p) transitions are examined for each ion. We find that the main contribution to the DR rate is from 2s-electron excitation (both ..delta..nnot =0 and ..delta..n = 0 processes), although the contribution from 1s excitation is found to be as large as 40% of the total rate at high temperatures. Finally, the effect of configuration mixing is examined for a group of dominant states and the effect on the overall rate is estimated.