Palladium-doped gold clusters. AunPd- (n = 1-4). were investigated using anion photoelectron spectroscopy at 4.66 eV photon energy. Electron affinities (EAs) and vertical detachment energies (VDEs) are determined, and the electronic structures of Pd-doped Au-n clusters are compared to those of pure Au-n clusters. A peak shape analysis reveals electronic and geometric similarity between Au-n(-) and Aun-1 Pd- clusters and it is found that (1) an electron promotion occurs from 4d to 5s orbital in the Pd atom, and that (2) the bond of Au-Pd is formed through sigma orbital between 6s of Au and 5s of Pd. (C) 2002 Published by Elsevier Science B.V.