Reexamining if long-lived N⁻ anions are produced in fast dissociative electron-capture collisions

The existence of long-lived states of N⁻ has been a topic investigated with conflicting experimental results. Highly excited spin-aligned states, however, were predicted to have long lifetimes and even be stable against autodetachment. We repeated the measurements of N⁻ formation in 0.9 MeV N₂+Ar charge-exchange collisions and found that the ions reported previously as N⁻ [ Heber et al. Phys. Rev. A 38 4504 (1988)] are an O⁻ fragment from a 0.9 MeV H₂NO⁺ impurity beam. This result adds to the comulating data indicating that N⁻ is not going to affect carbon dating measurements using accelerator mass spectrometry.