Electron-ion recombination rate coefficients, photoionization cross sections, and ionization fractions for astrophysically abundant elements. II. Oxygen ions

A comprehensive and self-consistent set of new atomic data for photoionization cross sections, sigma(PI), and total unified recombination rate coefficients, alpha(R)(T), of oxygen ions are obtained. The calculations are carried out in the close coupling approximation employing the R-matrix method. The unified treatment of total recombination includes both the radiative and dielectronic processes. The analysis of astrophysical spectra and ionization balance requires atomic data for all ionization stages of an element, and the accuracy depends on the self-consistency and completeness of data. In the present work the criterion of self-consistency between the rates for the inverse processes of photoionization and recombination is satisfied in an ab initio manner by employing an identical set of eigenfunction expansions in the calculations for both atomic processes. State-specific recombination rate coefficients are also presented for a large number of bound states. As a first application, the present alpha(R)(T) are used to obtain ionization fractions of oxygen ions in plasmas in coronal equilibrium. Ionization fractions in photoionization equilibrium can be readily obtained by employing the present data for the total sigma(PI) and for alpha(R)(T).