Modeling of the absorption profile of the 60 GHz band of atmospheric oxygen using the memory function formalism

Abstract

The profile of the oxygen absorption band centered at 60 GHz is modeled using the formalism of memory functions. The memory function determines the relation between the initial and final states of a molecule after its collision. The model profile takes into account the spectral exchange and contains two parameters, which depend on temperature and pressure. These parameters characterize the probabilities of spectral exchange between series of lines (branches) corresponding to molecular transitions of different types. To describe the absorption profile in the frequency range of 0–120 GHz in terms of the model proposed, the “+” and “−” branches of fine structure transitions and the series of nonresonance lines with frequencies on the order of 10−3–10−5 GHz are taken into account. The values of the parameters that take into account the spectral exchange are found from the condition of the best fit between the developed model profile and the profile calculated according to the millimeter-wave propagation model. The parameters found have physically substantiated and smooth temperature dependences, which confirms the adequacy of the model. The difference between these models does not exceed 2–3%, which corresponds to the declared uncertainty.