NIGHTGLOW EMISSIONS FROM OXYGEN IN THE LOWER THERMOSPHERE

Several independent trains of reasoning lead to the conclusion that O2(c1-SIGMA(u)-) is the precursor for the emission of the 557.7 nm line of atomic oxygen. It is shown that the measured altitude profile of the volume emission rate of the Herzberg I system is reproduced by using the expected rate coefficient for the production of O2(A3-SIGMA(u)+) by termolecular association and rate coefficients for quenching by atomic and molecular oxygen that accord with laboratory evidence, Termolecular association does not contribute directly to the Atmospheric system because the O2(b1-SIGMA(g)+) it generates is mainly in high vibrational levels and vibrational deactivation of these by interchange of electronic energy with normal oxygen molecules is not rapid enough to prevent deactivation to O2(a1-DELTA(g) or X3-SIGMA(g)-) from occurring. The prime source of the O2(b1-SIGMA(g)+, v = 0) is excitation of the O2(X3-SIGMA(g)-, v = 0) collision partner involved in O2(A3-SIGMA(u)+, A'3-DELTA(u) and c1-SIGMA(u)-) deactivation. This source can account for the measured altitude profile of the volume emission rate of the Atmospheric system.