Recombination coefficients for C II lines

Abstract

Effective recombination coefficients are given for C II transitions between doublet states. The calculations are carried out in the temperature range 500-20 000 K and for an electron density of 104 cm-3. The effects of electron collisions on the excited states are included. The necessary bound-bound and bound-free radiative data are obtained from a new R-matrix calculation in which photoionization resonances are fully delineated, thereby accurately incorporating the effects of both radiative and dielectronic recombination. The R-matrix calculation includes all bound states with principal quantum number n ≤ 15 and total orbital angular momentum L ≤ 4. The effect of moving the resonance features to their experimentally determined positions is also investigated and found to be important at low temperatures.