Ionization of metastable nitrogen and oxygen atoms by electron impact: Relevance to auroral emissions

Total cross sections are theoretically evaluated for electron impact ionization of initially metastable states of nitrogen as well as oxygen atoms, known to play roles in auroral emissions observed in the Earth's polar regions as also in the cometary coma and airglows. If the long-lived N(P-2), N(D-2), O(S-1), and O(D-1) metastable species get ionized in their interactions with energetic electrons, then they would not contribute to auroral emission. Therefore, we investigate electron ionization of the said metastable species by calculating relevant total cross sections. Our quantum mechanical calculations are based on projected approximate ionization contribution in the total inelastic cross sections. In all the four targets, the resulting cross sections are fairly large, indicating the importance of the electron ionization process.