Vibrational population distribution in the hydroxyl night airglow

Abstract

Relative populations of the vibrational levels ν = 2 to ν = 9 (except ν = 5) of the hydroxyl radical have been determined from observations of the Δν = 2 and 3 sequences of the vibration–rotation bands in the infrared night airglow spectrum using a Fourier transform spectrometer. The observed line intensities were corrected for water vapour absorption using a new technique. The results indicate a population of the upper vibrational levels which is as much as a factor of two lower than that found in other studies. The observed distribution is not consistent with the atomic hydrogen ozone reaction being the sole excitation mechanism in the night airglow unless the quenching and other rates used in our model are in error.