State-diagnosed charge stripping in low-energy collisions of ground-state and highly excited N⁺ ions with He

Abstract

Translational energy spectra have been measured on N²⁺ product ions resulting from 2-keV charge-stripping collisions between N⁺ions and He. The projectile N⁺ ion beam is produced under varying ion source conditions so as to contain different fractions of a long-lived metastable component. By measuring the endoergic energy defect for charge stripping from ground-state and excited-state projectiles at different electron energies in the ion source, the quantal identity of the N⁺ metastable state is deduced to be either 2s2p²2p' ¹D° , which lies 17.9 eV above the 2s²2p^{2 3}P ground electronic state, or 2s²2p3s ¹P°, whose excitation energy is 18.5 eV.