Dielectronic recombination of Fe²²⁺ and Fe²¹⁺

The author calculates dielectronic recombination rate coefficients for the Be-like and B-like ions Fe²²⁺ and Fe²¹⁺ using a multiconfiguration LS-coupling expansion and allowing for Delta n_c=0 and Delta n_c=1 autoionising transition into the continuum of excited states. The effect of intermediate coupling is also investigated and found to be less than 10%. They use autostructure-a general program for the calculation of multiconfiguration LS-coupling or intermediate-coupling autoionisation transition rates (incorporating superstructure)-to calculate the dielectronic recombination rate coefficient for the 1-2 and 2-3 core transitions. Together with the Burgess general formula for the 2-2 transition, they obtain about 95% of the total dielectronic recombination rate coefficient for ground state and look at its effect on the ionisation balance for a steady-state plasma. They confirm the recent findings of Smith et al. (1985) that the effect of Delta n_c=0 secondary autoionisation is much less significant for highly charged ions than was suggested by Jacobs et al.