The Einstein Coefficient for spontaneous emission of the O2(a¹Δg) state



Recently reported measurements of the absorption band strength (i.e., the Einstein B-coefficient for absorption) for the transition O2(X3Σg → a1Δg) at 1.27 µm, when correctly reanalyzed in this paper, indicate that the Einstein A-coefficient for spontaneous emission of radiation is 1.47 × 10−4 s−1. This is a factor of 1.75 smaller than the value of 2.58 × 10−4 s−1 that has been used almost exclusively in the aeronomy field for the past 30 years. The determination of the new A-value is reviewed, with an emphasis on the derivation of the appropriate ratio of the degeneracies of the upper and lower states of this transition. The new A-value implies that ozone concentrations as inferred from measurements of O2(a¹Δg) emission must be increased significantly in existing databases and also that the efficiency of solar heating in the Hartley band of ozone is larger than previously calculated.