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

The existence of long-lived states of N{sup -} 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{sup -} formation in 0.9 MeV N{sub 2}+Ar charge-exchange collisions and found that the ions reported previously as N{sup -} [ Heber et al., Phys. Rev. A 38, 4504 (1988) ] are an O{sup -} fragment from a 0.9 MeV H{sub 2}NO{sup +} impurity beam. This result adds to the comulating data indicating that N{sup -} is not going to affect carbon dating measurements using accelerator mass spectrometry.