A radiative transfer calculation involving complete frequency redistribution (CFR) in each line in the CO2 → 001 band, rotational redistribution in the 001 state, and an altitude independent 225° Doppler line width is used to calculate CO2 001 and N2‡ vibrational temperature altitude profiles. The υ-υ coupling between CO2 001 and N2‡ is accounted for. Excitation sources of the CO2 001 → N2‡ system include absorption of sunlight and earthshine by CO2 at 2.7 and 4.3 μm, N2‡ excitation via 5% efficient O(¹D) quenching by N2, the N + NO reaction, and photoelectrons. Excitation and quenching by intramolecular CO2 collisions and N2 collisions with H2O, O2‡, and O are also included. The CO2 001 → N2‡ vibrational temperature decouples noticeably from atmospheric kinetic temperature at about 60 km. The CO2 001 and N2‡ vibrational temperatures are identical below 85 km. At about 90 km the 001 and N2‡ vibrational temperatures decouple. Above 90 km the N2‡ vibrational temperature is strongly influenced by the υt reaction N2‡ + O ⇆ N2 + O and approaches the atmospheric kinetic temperature at nighttime, but it is somewhat higher in the daytime owing to the nonthermal sources of N2‡ excitation that are operative mainly in the daytime. The daytime CO2 001 vibrational temperature above about 80 km is found to be very nearly equal to that of a radiating blackbody surface that would produce a photon flux near 4.3 μm equal to that delivered onto the top of the earth's atmosphere by sunlight. The nighttime CO2 001 vibrational temperature above 60–70 km is mainly radiatively controlled by the transport of earthshine to space.
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Kumer et al. (1974) studied this question.