Dielectronic recombination in plasmas. II. Initial excited states - art. no. 046407

Ions in a plasma recombine with electrons by both direct and resonant modes . The latter, the dielectronic recombination, can be a dominant process at temperature near T=Z(2) Ry, for ions with charge Z. The rates are usually g iven for target ions in their ground states, and contributions from all dou bly excited intermediate states and final singly excited states of the reco mbined ions are summed over. To facilitate applications of the rates in pla sma modelling in terms of rate equations, simple rate formulas are often de vised. However, at finite temperature, a sizable fraction of ions is initia lly in an excited state, and after recombination, ions are usually left in singly excited final states. Thus new empirical rate formulas are needed th at exhibit an explicit dependence on final as well as initial states of the ions before and after the recombination. We have calculated properly adjus ted rates where (a) the target ions are allowed to be in their ground and e xcited states, and (b) contributions to the individual final states are exp licitly separated. Multiple cascades are important in such calculations. Fo r Al3+ ions we show that rates for the initial excited states are much larg er than that for the ground state.