Interaction of Sodium Atoms with Molecular Nitrogen in the Upper Atmosphere of the Earth

Abstract

In recent years numerous satellite data on the yellow glow of the sodium layer (located at an altitude of 85–95 km from the Earth’s surface) have become available. Studies of optical activity at sodium D‑line frequencies are necessary for a better understanding of the plasma-chemical processes occurring in the mesosphere. It should be taken into account that these processes occur in a neutral environment, where molecular nitrogen is the main component. In this study the analytical numerical expressions for the elements of a 3 × 3 matrix of the interaction between Na(²P_j) and N₂(\(X{}^{1}\Sigma _{g}^{ + }\)) and the interaction potential between Na(²S_1/2) and N₂(\(X{}^{1}\Sigma _{g}^{ + }\)) are obtained at medium and large interparticle distances that determine the collisional broadening of the radiation lines. The exchange, quadrupole–quadrupole, dispersion, and spin–orbit interactions are taken into account. The exchange interaction between the valence Na electron and N₂(\(X{}^{1}\Sigma _{g}^{ + }\)) molecule is described by the local Hellman pseudopotential. The effect of the overlap between Na(²S_1/2,²P_j) and N₂(\(X{}^{1}\Sigma _{g}^{ + }\)) electron densities is taken into account in the evaluation of long-range quadrupole–quadrupole and dispersion interactions.