Radiative association and inverse predissociation of oxygen atoms

The formation of ${\mathrm{O}}_2$ by radiative association and by inverse predissociation of ground-state oxygen atoms is studied using quantum-mechanical methods. Cross sections, emission spectra, and rate coefficients are presented and compared with prior experimental and theoretical results. At temperatures below 1000 K, radiative association occurs by approach along the 1 ${}_{}{}^3{}_{}{}^{}\mathrm{\Pi }_{\mathit{u}}^{}{}_{}{}^{}$ state of ${\mathrm{O}}_2$ and above 1000 K inverse predissociation through the B ${}_{}{}^3{}_{}{}^{}\mathrm{\Sigma }_{\mathrm{u}}^{\mathrm{-}}{}_{}{}^{}$ state is the dominant mechanism. This conclusion is supported by a quantitative comparison between the calculations and data obtained from hot oxygen plasma spectroscopy.