The excitation of the triplet lines of O2+ in nebulae

The excitation of the triplet lines of O²⁺ between 280 and 380 nm in nebulae is attributed to a combination of the Bowen fluorescence mechanism pumped by the He⁺ resonance line and charge transfer into excited states of O²⁺ in collisions of O³⁺ with neutral hydrogen atoms. The lines at 377.4 and 375.7 nm are due almost entirely to charge transfer population of the $$(2p\,3p)^{3}{D}_{1}$$ level. The close agreement obtained between the calculated and observed line intensities confirms the accuracy of the charge transfer rate coefficients.