State-selective single-electron capture in 30-keV N3+-He collisions

The cold-target recoil-ion momentum spectroscopy has been employed to study the single-electron-capture processes in collisions of N3+ ions with He atoms at an impact energy of 30 keV. From the longitudinal momentum spectrum of recoil ions, the different electronic configuration was identified, and the metastable projectile ions were distinguished. For the ground-state N3+(2s(2) S-1) projectile, the single-electron capture into the N2+(2s(2)2p P-2) state is the dominant reaction channel, whereas for themetastable-state N3+(2s2p P-3) projectile, the single-electron capture into the N2+(2s2p(2) D-2) state is the main reaction channel. The fraction of the metastable-state N3+(2s2p P-3) of the incident projectile beam is about 46%. The relative differential cross sections for the capture to different orbitals of N3+ ions are obtained and are compared with other experiments at low energy and the predictions of the classical over-the-barrier model.