OH A²Σ–X²π(0,0) band rotational line emission rate factors

The hydroxyl radical (OH) is an important species in the study of the Earth's ozone layer, because it moderates the catalytic destruction of ozone by odd halogens and odd nitrogen. The atmospheric distribution of OH can be deduced from measurements of the ultraviolet fluorescence emission of the (0,0) band of the OH ( A 2 Σ– X 2 π) system. The fluorescence emission is proportional to the product of a g factor and the OH density. Since synthetic spectral fitting of the rotational lines of the OH bands constitutes an important aspect of the measurement process used by some experimenters, accurate knowledge of the g factors for the discrete rotational lines is essential for an accurate retrieval of the OH concentration from observed spectra. We present here, for the temperatures 200.0, 240.0, 296.0, 300.0, and 500.0 K, (1) the g factor for the entire OH ( A 2 Σ– X 2 π)(0,0) band and (2) the individual g factors of each rotational line for the band. The derived g factor at 240 K for the entire band is (5.5±1.1)×10 −4 photon s −1 .