Photoelectron spectroscopy of negatively charged bismuth clusters: Bi-2, Bi-3, and Bi-4

We have recorded the 35 1 nm photoelectron spectra of Bi; , Bi; , and Bi; . The spectrum of Bi; shows transitions to at least seven electronic states of Bi, neutral, four of which are observed with vibrational resolution. Term energies, bond lengths, and vibrational frequencies are obtained for the anion ground state and for the first three excited states of Bi, . These results are compared to previous spectroscopic measurements and to the ab inifiu calculations presented in the accompanying paper. The photoelectron spectrum of Bi; reveals some of the electronic structure of Bi, and the results are discussed in comparison to recent theoretical work. Adiabatic electron affinities are obtained for Bi, [ 1.271(8) eV] and for Bi, [ 1.60(3) eV]. The electron affinity of Bi, is estimated from the onset of photodetachment to be 1.05( 10) eV.