Radiative-recombination cross sections and rate coefficients of atomic oxygen

Cross sections for radiative recombination of electrons with ground-state atomic oxygen ions to form oxygen atoms in the O[${(}^4$S)nl] ${}_{}{}^{3,5}{}_{}{}^{}$L states are calculated for nl up to (15,14) at 19 electron energies from 0.0345 to 2.585 eV based on Hartree-Fock wave functions of the bound and continuum states. By extrapolating the cross sections beyond n=15, the radiative-recombination rate coefficients are determined. The present cross sections are virtually identical to those obtained by using the hydrogenic approximation for l≥3, but entirely different for the ns and np series. For the nd series the agreement is good at low energies, but the discrepancy becomes larger at higher energies. The present calculation agrees with a calculation based on the quantum-defect method to within 10% for the nd series, but some discrepancy is found for the np series. In the case of the ns series these two sets of calculations disagree entirely.