ANALYSIS OF HYDROXYL EARTHLIMB AIRGLOW EMISSIONS - KINETIC-MODEL FOR STATE-TO-STATE DYNAMICS OF OH(V,N)

Detailed spectroscopic analysis of hydroxyl fundamental vibration-rota tion and pure rotation emission lines has yielded OH(upsilon,N) absolu te column densities for nighttime earthlimb spectra in the 20 to 110-k m tangent height region. High-resolution spectra were obtained in the Cryogenic Infrared Radiance Instrumentation for Shuttle (CIRRIS 1A) ex periment. Rotationally thermalized populations in upsilon=1-9 have bee n derived from the fundamental bands between 2000 and 4000 cm-1. Highl y rotationally excited populations with N less-than-or-equal-to 33 (le ss-than-or-equal-to 2.3 eV rotational energy) have been inferred from the pure rotation spectra between 400 and 1000 cm-1. These emissions o riginate in the airglow region near 85-90 km altitude. Spectral fits o f the pure rotation lines imply equal populations in the spin-rotation states F1 and F2 but a ratio PI(A'):PI(A'') = 1.8 +/- 0.3 for the A-d oublet populations. A forward predicting, first-principles kinetic mod el has been developed for the resultant OH(upsilon,N) limb column dens ities. The kinetic model incorporates a necessary and sufficient numbe r of processes known to generate and quench OH(upsilon,N) in the mesop ause region and includes recently calculated vibration-rotation Einste in coefficients for the high-N levels. The model reproduces both the t hermal and the highly rotationally excited OH(upsilon,N) column densit ies. The tangent height dependence of the rotationally excited OH(upsi lon,N) column densities is consistent with two possible formation mech anisms: (1) transfer of vibrational to rotational energy induced by co llisions with 0 atoms or (2) direct chemical production via H + O3 --> OH(upsilon,N) + O2.