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 ${\mathrm{N}}^{2+}$ product ions resulting from 2-keV charge-stripping collisions between ${\mathrm{N}}^{+}$ ions and He. The projectile ${\mathrm{N}}^{+}$ 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 ${\mathrm{N}}^{+}$ metastable state is deduced to be either 2s2${\mathit{p}}^{2}$2p' $^{1}$D\ifmmode^\circ\else\textdegree\fi{}, which lies 17.9 eV above the 2${\mathit{s}}^{2}$2${\mathit{p}}^{2}$ $^{3}$P ground electronic state, or 2${\mathit{s}}^{2}$2p3s $^{1}$P\ifmmode^\circ\else\textdegree\fi{}, whose excitation energy is 18.5 eV.