O2 infrared radiation in the twilight airglow

A procedure was developed to predict the emission spectrum of the O2 (0,0) infrared atmospheric band in the airglow at any specified observation site in the lower atmosphere. A photochemical model of the atmosphere between 50 and 100 km altitude was used to estimate the number density of O2 (a1Δ/sub g/) molecules, and the volume emission rate for photons in the O2(0,0) band. A model of the photon emission processes was used to distribute the photons among the spectral lines of the band. The absorption in the lower atmosphere was computed by use of an absorption line shape obtained by a convolution of the Doppler and Lindholm profiles. The lower atmosphere was approximated by a set of concentric strafified layers with each layer considered to have constant temperature and pressure. Where possible, the initial calculation results were stored for use as precomputed values for repeated spectral calculations. The procedure was used to predict spectra for the O2(0,0) band for 18 times during the evening twilight transition of September 30, 1976 at Utah State University, Logan, Utah. The predicted spectra were compared with observed spectra obtained using Fourier spectroscopy during the same evening. The interferograms for the spectra were recorded from the output of a field-widened interferometer-spectrometer