State-selective stepwise two-photon detachment study of the Be- ion

The presence of two metastable states in the negative beryllium ion, 2s2p(2 4)P and 2p(3 4)S, which are connected by an optical transition, offers a unique possibility for gaining new information about this ion. Utilizing resonant, two-photon detachment, combined with resonant-ionization detection of the resulting neutral atoms, we have obtained results yielding the lifetimes of the P-4(1/2) (0.73 +/- 0.08 mu s) and P-4(5/2) (0.33 +/- 0.06 mu s) levels, the fine-structure splittings of the P-4(J) levels, and an improved P-4-S-4 transition wavelength.