Relative Stability of Small Silver, Platinum, and Palladium Doped Gold Cluster Cations

The stability patterns of single silver, platinum, and palladium atom doped gold cluster cations, MAu_{N-1}^+ (M= Ag, Pt, Pd; N = 3-6), are investigated by a combination of photofragmentation experiments and density functional theory calculations. The mass spectra of the photofragmented clusters reveal an odd-even pattern in the abundances of AgAu_{N-1}^+, with local maxima for clusters containing an even number of valence electrons, similarly to pure Au_N^+. The odd-even pattern, however, disappears upon Pt and Pd doping. Computed dissociation energies agree well with the experimental findings for the different doped clusters. The effect of Ag, Pt, and Pd doping is discussed on the basis of an analysis of the density of states of the N = 3-5 clusters. Whereas Ag delocalizes its 5s valence electron in all sizes, this process is size-specific for Pt and Pd.