Observation of 5S nitrogen metastable state in charge exchange collisions

The charge-transfer reactions of excited metastable nitrogen atomic ions with argon are reported. The principal contributor to the reaction cross section is N+(2s,2p3; 5S) while small contributions are made by the 1S and 3P states of N+. The experiment quite uniquely allows a clear identification of the specific electronic state which undergoes a charge-transfer reaction. Excited atomic nitrogen ions are important in interstellar and synthetic plasmas. The N+(5S) state is thought to be responsible for auroral emissions in the ultraviolet.