Model of daytime emissions of electronically-vibrationally excited products of O₃ and O₂ photolysis: application to ozone retrieval

Abstract. The traditional kinetics of electronically excited products of O₃ and O₂ photolysis is supplemented with the processes of the energy transfer between electronically-vibrationally excited levels O₂(a¹Δ_g, v) and O₂(b¹Σ⁺_g, v), excited atomic oxygen O(¹D), and the O₂ molecules in the ground electronic state O₂(X³Σ_g⁻, v). In contrast to the previous models of kinetics of O₂(a¹Δ_g) and O₂ (b¹Σ⁺_g), our model takes into consideration the following basic facts: first, photolysis of O₃ and O₂ and the processes of energy exchange between the metastable products of photolysis involve generation of oxygen molecules on highly excited vibrational levels in all considered electronic states – b¹Σ⁺_g, a¹Δ_g and X³Σ_g⁻; second, the absorption of solar radiation not only leads to populating the electronic states on vibrational levels with vibrational quantum number v equal to 0 – O₂(b¹Σ⁺_g, v=0) (at 762 nm) and O₂(a¹Δ_g, v=0) (at 1.27 µm), but also leads to populating the excited electronic–vibrational states O₂(b¹Σ⁺_g, v=1) and O₂(b¹Σ⁺_g, v=2) (at 689 nm and 629 nm). The proposed model allows one to calculate not only the vertical profiles of the O₂(a¹Δ_g, v=0) and O₂(b¹Σ_g, v=0) concentrations, but also the profiles of [O₂(a¹Δ_g, v≤5)], [O₂ (b¹Σ⁺_g , v=1, 2)] and O₂(X³Σ_g⁻, v=1–35). In the altitude range 60–125 km, consideration of the electronic-vibrational kinetics significantly changes the calculated concentrations of the metastable oxygen molecules and reduces the discrepancy between the altitude profiles of ozone concentrations retrieved from the 762-nm and 1.27-µm emissions measured simultaneously.