5 Conclusions

The energy levels of C ⁺ doublet bound states with $n \leq 15$, $L \leq 4$ were calculated using the R-matrix method. Photoionization cross-sections for these states were computed using a variable step energy mesh ensuring the correct mapping of resonances. The importance of correctly delineating the autoionizing resonances in the photoionization cross-sections was demonstrated by considering the area under the cross-section. In the case of 2s2p^2 2D$\rm ^e$, this area differs by factor of 3 comparing our data with those from the OP (Yu Yan & Seaton [1987]).

We find that moving the two energetically lowest resonances to the experimental positions in the appropriate cross-sections significantly increases their contribution to the recombination coefficients, particularly at low temperatures.

The effective recombination coefficients for lines of C II have been tabulated in the temperature range $T_{e} = 500 - 20\,000$ K and at electron density N_e = 10⁴ cm^-3. The use of atomic data of high quality for bound-bound and bound-free radiative processes among all the terms with $n \leq 15$ means that the results given here are expected to be more reliable than any previous work.