Electronic level structure of group III heavy element clusters studied by photoelectron spectroscopy

UV-photoelectrons of mass-defined indium and thallium cluster anions have been analyzed at a detachment energy of 3.68eV in the size range n = 2-20. The photoelectron threshold energies are in rough agreement with the values predicted by the metal droplet model. A number of low-lying excited states of the neutral-clusters are detected. The high atomic s-orbital binding energies appear to induce alkali-like character of In; and Tl, .