Calculated OH A~2#SIGMA#~+ - X~2#PI# (0,0) band rotational emission rate factors for solar resonance fluorescence

摘要

The Middle Atmosphere High-Resolution Spectrograph Investigation (MAHRSI) measured vertical density profiles of hydroxyl (OH) by observing OH A~2#SIGMA#~+ - X~2#PI# (0,0) solar resonance fluorescence in the mesosphere near 309 nm [Conway et al., this issue]. Interpretation of the MAHRSI results requires calculation of the OH(0,0) rotational emission rate factors (g factors) which describe the molecule's fluorescent scattering efficiency. This calculation relies heavily on a solar irradiance measurement with high enough spectral resolution to identify the amount of excitation for each rotational transition (resolving power > 3.1 * 10~5). Recent high-resolution ground-based measurements of the solar irradiance and more accurate absolute solar irradiance observations allow for much more accurate g factors. We find that the relative intensities of calculated OH(0,0) rotational g factors are in excellent agreement with MAHRSI spectra. The calculated OH(0,0) band g factor is found to be 3.51 * 10~(-4) s~(-1) at 200 K, in good agreement with the most recent work on the subject.