Charge exchange and metastability of small multiply charged gold clusters

Charge-exchange and fragmentation cross-section measurements on Au₂²⁺, Au₃²⁺, Au₄²⁺ and Au₄³⁺ are presented. Limits on the cluster electron affinities are obtained in terms of the ionization energies of Ar, N₂, Kr, CO, Xe, and O₂. Fragmentation cross sections, largely independent of the gas species, are comparable to those for charge exchange. The metastability of Au₂²⁺ is shown to be implied by the lower bound on its electron affinity.