Resonant Ionization Spectroscopy of Ba-: Metastable and Stable Ions

A new technique based on the combination of laser photodetachment and resonance ionization spectroscopy has been used to characterize the state composition of a fast, negative-ion beam of barium and to determine the binding energies of its long-lived components, the metastable 5d6s6p F9/24 state and the 6s26p P3/2,1/22 ground state, with an accuracy previously inaccessible for the weakly bound, negative alkaline-earth ions. Additional information about the Ba- states was obtained from lifetime studies in the ASTRID storage ring.