Large-scale calculation of dielectronic recombination parameters for Mg-like Fe

Energy levels, radiative transition probabilities and autoionization rates for 1s22s22p63l'nl (n = 3–12, l ≤ n − 1) and 1s22s22p64l'nl (n = 4–7, l ≤ n − 1) states in Mg-like iron (Fe14+) are calculated by the Hartree–Fock-relativistic method (Cowan code) and the relativistic many-body perturbation theory method (RMBPT code). Autoionizing levels above three thresholds 1s22s22p63s, 1s22s22p63p and 1s22s22p63d are considered. It is found that configuration mixings [3sns + 3pnp + 3dnd] and [3snp + 3pns + 3pnd + 3dnp] play an important role for all atomic characteristics. Branching ratios relative to the first threshold and intensity factors are calculated for satellite lines, and dielectronic recombination (DR) rate coefficients are determined for the excited 444 odd-parity and 419 even-parity states. It is shown that the contribution of the highly-excited states is very important for calculation of total DR rates. Contributions from the excited 1s22s22p63l'nl states with n ≥ 12 and 1s22s22p64l'nl states with n ≥ 7 to DR rate coefficients are estimated by extrapolation of all atomic parameters. The total DR rate coefficient is derived as a function of electron temperature.