Two states of CO- which are expected to live longer than the well-known (2)
Pi shape resonance are examined and the results obtained are compared with
the analogous states of the isoelectronic N-2(-) system. The (4)Sigma(-) an
d (4)Pi states are found to be stable with respect to dissociation. The lat
ter state is also stable with respect to single-electron loss to its parent
neutral state. The lifetime of this state is supposed to be long, but not
necessarily long enough to allow detection in a mass spectrometer.