Simultaneous measurements of OH(9,4), (8,3), (7,2), (6,2) and (5,1) bands in the airglow

Abstract

Band intensities and the rotational temperatures for the OH(9,4), (8,3), (7,2), (6,2) and (5,1) bands have been measured by means of a multichannel tilting filter photometer at Cachoeira Paulista (22.7°S, 45.0°W), Brazil. It is observed that the nocturnal variations of the five bands show good correlation between them but that there are small differences in the amplitudes of the variations between the bands from the upper vibrational levels and those from the lower levels. Studies of the cross correlation between the band intensities show that the nocturnal variations of the upper vibrational bands lead those of the lower levels. Vibrational populations and initial excitation rates for each vibrational level are calculated. The results show an increase of the initial excitation rate in the v=5 and v=6 levels. The different features of the intensity variations and the excitation rates of the lower vibrational levels suggest the existence of the mechanism HO2 + O → OH* + O2, capable of exciting OH to the v=5 and v=6 levels, in addition to the principal mechanism, assumed to be the reaction H + O3 → OH* + O2. The rotational temperatures derived from the ratios between the Q and R branches show good agreement between the different bands, indicating a high degree of rotational relaxation by thermal collisions.