LONG-LIVED, DOUBLY-CHARGED DIATOMIC AND TRIATOMIC MOLECULAR-IONS

Lifetimes of doubly charged diatomic and triatomic molecules have been measured by monitoring the decay curves of such ions in a heavy-ion s torage ring. CO2+, N-2(2+), CO22+, CS22+ and SH2+ are all found to pos sess long-lived components which survive for time periods greater than a few seconds. All these dications are found to be essentially stable and their ultimate destruction is due to interactions with residual g ases in the ring. CO2+ possesses many more lifetime components in the millisecond range than the isoelectronic N-2(2+) ion. Translational en ergy spectrometry experiments on the latter species also fail to revea l any short-lived (microsecond) components. Ab initio configuration in teraction calculations have been carried out and the potential energy curve for the lowest-energy metastable state of N-2(2+) ((1) Sigma(g)) has been determined, along with Franck-Condon factors for vertical tr ansitions to different vibrational levels from the ground state of neu tral N-2; tunnelling times of each vibrational level have been compute d.