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 ${\mathrm{O}}^{5+}$, ${\mathrm{Ar}}^{15+}$, ${\mathrm{Fe}}^{23+}$, and ${\mathrm{Mo}}^{39+}$ at several electron temperatures for the initial state $1s^{2}2s$. The autoionizing and radiative transition probabilities are computed with single-configuration, nonrelativistic Hartree-Fock wave functions and $\mathrm{LS}$ coupling. All possible Rydberg autoionizing states and their cascades are included. The relative contributions to the total DR rate of the $1s$, $2s\left(\Delta n\ne 0\right)$, and $2s(\Delta n=0;2s\to 2p)$ transitions are examined for each ion. We find that the main contribution to the DR rate is from $2s$-electron excitation (both $\Delta n\ne 0$ and $\Delta n=0\mathrm{}$ 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.