Association of atomic oxygen and airglow excitation mechanisms

An outline is presented of a method of calculating relative rates of association of oxygen atoms by energy transfer into the different bound states of molecular oxygen. The method takes account of the detailed form of the potential energy curves for the different states. Results are presented for seven bound states of O₂ at temperatures between 100 and 600 K and are compared with laboratory and airglow data. The ⁵Π_g state, not known experimentally, accounts for over 70% of the total association below 200 K. At higher temperatures it is redissociated, and the variation in its effective association rate is primarily responsible for the variation of the total rate of oxygen association with temperature. The ⁵Π_g state is probably involved in the production at night of the a¹Δ_g and b¹Σ_g⁺ states of O₂, and in the production of $\text{O(}{}^1\text{S)}$ in the airglow. It may also be produced by electron impact on O₂, and contribute to $\text{O(}{}^1\text{S)}$ production in aurorae.