5 Conclusion

Effective recombination coefficients for the formation of OIII lines in the 5g - 4f transition array have been calculated in the intermediate coupling scheme at temperatures and densities appropriate to nebular plasmas. The temperature and density dependence of the effective recombination coefficients has been factorized to permit the coefficients to be fitted. We have given formulae to enable the line effective recombination coefficients to be computed for any particular 5g level of O²⁺ as a function of electron temperature $T_{\mathrm e}$ and electron density $N_{\mathrm e}$. Some of the lines of the 5g - 4f transition array are sensitive to the electron density of the emitting region, and might be suitable as a density diagnostic in objects where the abundance of O³⁺ is relatively large.