“…The volume emission rate (VER, in photons/cm 3 /s) is the integration of r g over the entire band, and the O 2 ( a 1 Δ g ) number density is just the VER divided by the electronic‐vibrational Einstein A coefficient (2.27 × 10 −4 s −1 , calculated from HITRAN2016 individual line intensities using equations 18 and 32 from Gamache & Goldman, ). The O 2 a 1 Δ g state has a long lifetime (73 min), which assures that the molecule is in rotational equilibrium with the ambient atmosphere (Kaufmann et al, ). A simplified assumption is that r g scales with the absorption cross section: where S i j ( T ) is the line intensity for transition i j and f ( ν , ν i j , T , p ) is the normalized line shape function.…”