Stability and dissociation pathways of doped Au_nX⁺ clusters (X = Y, Er, Nb)

Size dependent stabilities, fragmentation pathways and dissociation energies of a series of gas phase cationic doped gold clusters, Au_nX⁺ (3 ≤ n ≤ 20; X = Y, Er and Nb), and pure Au_n⁺ clusters were investigated in photofragmentation experiments. Size dependent stability patterns were obtained and the branching between monomer and dimer evaporation was studied. For bare gold, the competing neutral monomer and dimer evaporation channels were found to be in agreement with earlier studies. For doped clusters, monomer evaporation is the most likely fragmentation channel with the exception of Au₁₈Y⁺ and Au₂₀Y⁺ for which gold dimer evaporation is also observed. Relations between the evaporative activation energies and both the experimental abundances and the fragment yield were derived based on unimolecular rate constants. The dissociation energies from this analysis show an odd–even staggering and enhanced stabilities for certain cluster sizes, in agreement with simple electronic shell model predictions.