Abstract. Close-coupling (CC) calculations of electron-ion recombination cross sections using the R-matrix method are presented and benchmarked with available experimental measurements. The electron-ion recombination process, including resonant and non-resonant recombination may be unified as a natural extension of the coupled-channel approximation, as traditionally employed for photoionization and electron-ion scattering. Recombination cross sections can be calculated to the same accuracy by employing similar eigenfunction expansions for the target ion. Detailed results are obtained for electron recombination with C V, C VI, O VIII and Fe XXV. Several sets of theoretical calculations are reported and discussed: non-relativistic CC in LS coupling, relativistic CC in the Breit-Pauli approximation, with radiative attenuation and fine structure, and the relativistic distorted-wave approximation. The theoretical results are in very good agreement with highly accurate experimental measurements at the Heidelberg test storage ring for C V, C VI and O VIII, and the electron-ion beam trap at Livermore for Fe XXV. We discuss the overall effect of radiation damping of all resonances on effective cross sections and rates, important for H-and He-like ions. In addition to agreement with experimental data, the validity of the CC calculations is demonstrated by the continuity between the calculated photorecombination, dielectronic recombination and electron impact excitation cross sections. Certain issues related to the works of

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AbstractvVe present a review of our fully relativistic approach to calculating atomic data charged ions, highlighting a research effort that spans years. Dediscussions of both theoretical and numerical techniques are provided. Our basic approach is expected to provide accurate results for ions that range from approximately half ionized to fully stripped. Options for improving the accuracy and range of validity of this approach are also discussed. In developing numerical methods for calculating data within this framework, considerable emphasis is placed on techniques that are robust efficient. A of fundamental processes are considered including: photoexcitation, electron-impact excitation, electron-impact ionization, autoionization, electron capture, photoionization and photorecombina tion. Resonance contributions to a variety of these processes are also considered, including discussions of autoionization, electron capture and dielectronic recombi nation. Ample numerical examples are provided in order to illustrate the approach and to demonstrate its usefulness in providing data for large-scale plasma modeling.

The range of conditions for which inclusion of the generalized Breit interaction is important in calculating the scattering matrix elements for 1s ionization is explored within the relativistic distorted-wave approximation. This approach is applied to the calculation of 1s ionization cross sections for a variety of ions with one to four bound electrons and nuclear charge Z in the range of 10рZр92. These data are then interpolated with simple, but accurate, fit formulas. The resulting expressions are readily integrated over a relativistic Maxwellian electron distribution function to obtain rate coefficients for plasma modeling. A discussion of the high energy behavior of the cross sections for large Z is also given.