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 O⁵⁺, Ar¹⁵⁺, Fe²³⁺, and Mo³⁹⁺ at several electron temperatures for the initial state 1s²2s. 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(Δn≠0), and 2s(Δn=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 Δn≠0 and Δn=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.