The electronic structures of binary gold cluster anions: AunM- (M = Pd, Ni, Zn, Cu, Mg) were investigated by anion photoelectron spectroscopy at the photon energy of 4.66 eV. The spectra exhibit even-odd alternation of electron affinities and characteristic spectral changes with n, which are accountable in terms of the interactions between the Au clusters and doped metal atoms. For the binary clusters containing Pd, Ni, and Cu. their valence electrons are shared with those of the Au clusters, whereas for Mg the doped atom is weakly bound to Au clusters. A size-dependent spectral change is clearly observed for AunPd- at n approximate to 5. (c) 2006 Elsevier B.V. All rights reserved.