Nightglow vibrational distributions in the A<sup>3</sup>Σ<sub>u</sub><sup>+</sup> and A'<sup>3</sup>Δ<sub>u</sub> states of O<sub>2</sub> 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 O 2 (A 3 + u ) and O 2 (A 3 u ) states from rotationally-resolved Herzberg I and Chamberlain band emissions in the terrestrial nightglow. The A 3 + 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 3 u and A 3 + 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 0.25 eV below the O( 3 P)+O( 3 P) dissociation limit. We compare these Herzberg state distributions with that of the O 2 (b 1 + g ) state, concurring with others that the intense nightglow emission associated with b 1 + g (v=0) is a reflection of direct transfer from the Herzberg states. This process takes place following O 2 collisions, with simultaneous production of very high a 1 g and b 1 + g vibrational levels.