Long-lived high-spin states of small anions:: 6II state of CO-

Stimulated by recent mass spectrometric observations, we have investigated several high-spin states of CO- to identify the observed anionic state. We follow a general construction principle for long-lived anionic states of small molecules: A possibly long-lived anionic state possesses several "equivalent" valence electrons bound to a positively charged ion core. Applying this idea to CO-, we have found a On state which is stable with respect to both single-electron emission and dissociation. Since all different decay channels are spin forbidden, this state is long-lived, and will be observable in a mass spectrometer. [S1050-2947(99)06504-X].