Unified electronic recombination of Ne-like Fe XVII: Implications for modeling X-ray plasmas

Unified recombination cross sections and rates are computed for (e + Fe XVIII) --> Fe XVII including nonresonant and resonant (radiative recombination [RR] and dielectronic recombination [DR]) processes in an ab initio manner with relativistic fine structure. The highly resolved theoretical cross sections exhibit considerably more resonance structures than observed in the heavy-ion storage ring measurements at Heidelberg, Germany. Nonetheless, the detailed resonance complexes agree well with experimental results, and the unified rates agree with the sum of experimentally derived DR and theoretical RR rates to similar to 20%, within experimental or theoretical uncertainties. Theoretical results may provide estimates of field ionization of Rydberg levels close to the DR peak and non-resonant background contributions particularly close to the RR peak as E --> 0. More generally, the unified results avoid the physical and practical problems in astrophysical models inherent in the separation of electronic recombination into RR and DR on the one hand and further subdivision into low-energy Deltan = 0 DR and high-energy Deltan > 0 DR in photoionized and collisionally ionized X-ray plasmas on the other hand.