Electron‐Ion Recombination Rate Coefficients and Photoionization Cross Sections for Astrophysically Abundant Elements. VII. Relativistic Calculations for O vi and O vii for Ultraviolet and X‐Ray Modeling

Aimed at ionization balance and spectral analysis of UV and X-ray sources, wepresent self-consistent sets of photoionization cross sections, recombinationcross sections, and rate coefficients for Li-like O VI and He-like O VII.Relativistic fine structure is considered through the Breit-Pauli R-matrix(BPRM) method in the close coupling approximation, implementing the unifiedtreatment for total electron-ion recombination subsuming both radiative anddi-electronic recombination processes. Self-consistency is ensured by using anidentical wavefunction expansion for the inverse processes of photoionizationand photo-recombination. Radiation damping of resonances, important for H-likeand He-like core ions, is included. Compared to previous LS coupling resultswithout radiative decay of low-n (<= 10) resonances, the presents results showsignificant reduction in O VI recombination rates at high temperatures. Inaddition to the total rates, level-specific photoionization cross sections andrecombination rates are presented for all fine structure levels n (lSLJ) up ton <= 10, to enable accurate computation of recombination-cascade matrices andspectral formation of prominent UV and X-ray lines such as the 1032,1038 Adoublet of O VI, and the `triplet' forbidden, intercombination, and resonanceX-ray lines of O VII at 22.1, 21.8, and 21.6 \ang respectively. Altogether,atomic parameters for 98 levels of O VI and 116 fine structure levels of O VIIare theoretically computed. These data should provide a reasonably complete setof photoionization and recombination rates in collisional or radiativeequilibrium.Comment: 33 pages, 8 figures, submitted to ApJ