Calculated zenith intensity of the second positive band of molecular nitrogen

Abstract

This note presents the result of our calculations of the zenith intensity of the second positive band of molecular nitrogen in the day glow. We also compare our theoretical calculations with the experimental results of Barth and Pearce [1965]. The second positive band of molecular nitrogen is the result of the spontaneous de-excitation of the molecule from the C3Πu to the B3Πg state. The C3Πu state is populated, in effect, only by electron impact excitation, since the spin forbidden character of the transition from the ground state makes the electric dipole transition probability very small. As the excitation threshold is approximately 10 ev, excitation due to thermal electrons is negligible; for this reason we considered only excitation by photoelectrons in our calculations.