Energy-resolved collision-induced dissociation of Cun+ (n=2-9):: Stability and fragmentation pathways

Collision induced dissociation of Cu-n(+) clusters (n = 2-9) in collision with Xe is presented in the center-of-mass energy range from about 100 meV to above 15 eV. The collision energy dependence is measured for the total and the partial dissociation cross sections, and the dissociation thresholds for the dominating processes are derived. The threshold energies show pronounced odd-even alternations, reflecting a higher stability of the odd-numbered, Cu-2n+1(+), clusters. Further, the evaporation of a single neutral atom is found to be the energetically favorable process for the even-numbered clusters, while the loss of the neutral dimer is favorable in the case of the odd-numbered clusters. An exception is Cu-9(+), where the formation of Cu-n-1(+) is energetically favorable, and the energetics of the Cu-n-2(+) formation are in good agreement with sequential evaporation of two neutral monomers. Here we discuss the energy dependency of the total and partial dissociation cross sections, and try to give a consistent picture of the dissociation dynamics. We present binding energies for the cationic clusters from their dissociation thresholds, and use those, in combination with the literature values for the ionization potentials of Cu-n, to estimate the binding energies for neutral copper clusters. Finally, we compare this work to earlier theoretical calculations, as well as experimental estimations of the binding energies. (C) 2000 American Institute of Physics. [S0021-9606(00)02010-9].