Dielectronic recombination as a direct free-bound radiative process

Abstract

The process of dielectronic recombination is studied in terms of the standard treatment of a free-bound dipole radiative transition between stationary states. The initial free state of electron-ion resonant elastic scattering is analysed using the Fano formulation for discrete-state-continuum configuration mixing. The n to infinity divergence in the energy-averaged partial dielectronic recombination cross sections, which arises in the isolated- resonance approximation, is eliminated by requiring continuity with the partial excitation cross sections at the excitation threshold. Detailed calculations for Mg+(3s-3p), Ca+(4s-4p), B2+(2s-2p) and C3+(2s-2p) are compared with experimental results. In most cases there is reasonable overall qualitative agreement, but uncertainties in the final-state distributions involved in the measurements prevent a fully quantitative comparison. The effects of external fields on the dielectronic recombination process are also discussed in the context of the present method.