Dielectronic recombination in plasmas: The final state distribution

The dielectronic recombination rate is one of the important input parameter s to rate equations for modeling plasmas, where the excited state populatio n of the plasma ions is determined by taking into account the radiative and collisional effects of plasma particles. The rates are often conveniently summarized in the form of empirical formulas to facilitate their use; in pa rticular, properly designed rate formulas are needed that describe the elec tron capture to the individual singly excited final recombined states. Howe ver, the currently available rate formulas fail to meet this requirement, a lthough they are obtained from more detailed benchmark calculations that ex plicitly include all the important transitions. The modified rate formulas may be obtained by keeping separate the rates to the individual singly exci ted final states, but still summing the contributions from different interm ediate resonance states, with proper account of the cascades. Ne-like Al3ions in their ground state are used as examples to show that the rates to t he final ground state are reduced by as much as a factor of 5 from the tota l rates.