Consistency check for OH(v = 9) density

We can examine whether the OH(v = 9) number density implied by the calculations of the OH(v = 9) + O O2 AB emission source is realistic. Some relevant information is available because ETON payload P228H obtained the emission profile of the (8,3) OH Meinel band (49). Figure S1 presents the OH(v = 8) concentration as a function of altitude, inferred from the P228H (8,3) OH Meinel band emission measurement using an Einstein coefficient of 0.9336 s−1, reported by Xu et al. (22). The figure also presents the calculated [OH(v = 9)] using Eq. M10. For this calculation, the second O-atom measurement (P234H) was used as input because it is the closest one in time—the (8,3) OH band emission was measured ~26 min before P234H and 100 min after P232H (first O-atom measurement). The integrated OH(v = 8) population corresponding to the ETON observation is approximately 50% larger than that calculated for OH(v = 9), in very good agreement with observations of the OH(8)/OH(9) ratio for the Meinel band emission reported in the literature (12, 14, 50).