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

Abstract

Abstract. Astronomical sky spectra from the Keck I telescope on Mauna Kea have been used to obtain vibrational distributions in the O2A3Σu+) and O2(A'3Δu) states from rotationally-resolved Herzberg I and Chamberlain band emissions in the terrestrial nightglow. The A3Σu+ 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'3Δu and A3Σu+ 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(b1Σg+) state, concurring with others that the intense nightglow emission associated with b1Σg+(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 a1Δg and b1Σg+ vibrational levels.