Monte Carlo studies of the resonance fluorescence technique for atmospheric atomic oxygen measurements

Abstract

The resonance fluorescence of the O (3P3S) triplet has been used extensively for rocket-borne measurements of atomic oxygen in the mesosphere and lower thermosphere. The accuracy and compatibility of different experimental configurations are however still a subject of controversy. In order to better quantify the measurements, we have developed a 3-dimensional Monte Carlo model which simulates the radiative transfer inherent to atom detection by means of resonance lamps. Angle-dependent partial frequency redistribution describes the fluorescence process, natural broadening becoming significant when the line center optical thickness exceeds 10. Applying the model to a recently flown rocket instrument, a strong temperature dependence and nonlinear relations between atomic oxygen abundance and fluorescence signal are found at densities above 5.1010 cm−3. Above 1.1012 cm−3, the signal gradually saturates and useful measurements cannot be obtained. The spatial distribution of the scattering events and effects of the payload motion are analyzed. A discussion of the results is applied to different calibration techniques for rocket instruments.