Nightglow vibrational distributions in the A³Σ_u⁺ and A'³Δ_u states of O₂ derived from astronomical sky spectra

Abstract. Astronomical sky spectra from the Keck I telescope on Mauna Kea have been used to obtain vibrational distributions in the O₂A³Σ_u⁺) and O₂(A'³Δ_u) states from rotationally-resolved Herzberg I and Chamberlain band emissions in the terrestrial nightglow. The A³Σ_u⁺ distribution is similar to that presented in earlier publications, with the exception that there is significant population in the previously undiscerned v=0 level. The vibrational distributions of the A'³Δ_u and A³Σ_u⁺ states are essentially the same when comparison is made in terms of the level energies. The intensity of Chamberlain band emission at the peak of the distribution is about one-fourth that of the Herzberg I emission, as previously shown, and may be related primarily to radiative efficiency. The peaks in both population distributions are about 0.25eV below the O(³P)+O(³P) dissociation limit. We compare these Herzberg state distributions with that of the O₂(b¹Σ_g⁺) state, concurring with others that the intense nightglow emission associated with b¹Σ_g⁺(v=0) is a reflection of direct transfer from the Herzberg states. This process takes place following O₂ collisions, with simultaneous production of very high a¹Δ_g and b¹Σ_g⁺ vibrational levels.