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

Collision induced dissociation of Cu-n(+) clusters (n = 2-9) in collision w ith Xe is presented in the center-of-mass energy range from about 100 meV t o above 15 eV. The collision energy dependence is measured for the total an d the partial dissociation cross sections, and the dissociation thresholds for the dominating processes are derived. The threshold energies show prono unced odd-even alternations, reflecting a higher stability of the odd-numbe red, Cu-2n+1(+), clusters. Further, the evaporation of a single neutral ato m 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 t he odd-numbered clusters. An exception is Cu-9(+), where the formation of C u-n-1(+) is energetically favorable, and the energetics of the Cu-n-2(+) fo rmation are in good agreement with sequential evaporation of two neutral mo nomers. Here we discuss the energy dependency of the total and partial diss ociation cross sections, and try to give a consistent picture of the dissoc iation dynamics. We present binding energies for the cationic clusters from their dissociation thresholds, and use those, in combination with the lite rature values for the ionization potentials of Cu-n, to estimate the bindin g energies for neutral copper clusters. Finally, we compare this work to ea rlier theoretical calculations, as well as experimental estimations of the binding energies. (C) 2000 American Institute of Physics. [S0021-9606(00)02 010-9].