Electron‐Ion Recombination Rate Coefficients and Photoionization Cross Sections for Astrophysically Abundant Elements. V. Relativistic Calculations for Fe xxiv and Fe xxv for X‐Ray Modeling

Photoionization and recombination cross sections and rate coefficients arecalculated for Li-like Fe XXIV and He-like Fe XXV using the Breit-PauliR-matrix (BPRM) method. A complete set of total and level-specific parametersis obtained to enable X-ray photoionization and spectral modeling. The abinitio calculations for the unified (e + ion) recombination rate coefficientsinclude both the non-resonant and the resonant recombination (radiative anddi-electronic recombination, RR and DR, respectively) for (e + Fe XXV) -> FeXXIV and (e + Fe XXVI) -> Fe XXV. The level specific rates are computed for allfine structure levels up to n = 10, enabling accurate computation ofrecombination-cascade matrices and effective rates for the X-ray lines. Thetotal recombination rate coefficients for both Fe XXIV and Fe XXV differconsiderably, by several factors, from the sum of RR and DR rates currentlyused to compute ionization fractions in astrophysical models. As thephotoionization/recombination calculations are carried out using an identicaleigenfunction expansion, the cross sections for both processes aretheoretically self-consistent; the overall uncertainty is estimated to be about10-20%. All data for Fe XXIV and Fe XXV (and also for H-like Fe XXVI, includedfor completeness) are available electronically.Comment: 31 pages, 10fug