The fragmentation pathways and dissociation energies of copper cluster cations, Cu-n(+) and Cu-n(2+), are determined by multiple-collision induced dissociation. For singly charged clusters, an odd-even staggering is observed throughout the investigated size range, 2 less than or equal ton less than or equal to 25, where the odd-size clusters have a higher dissociation energy than the average value of their even-size neighbors. The odd-even effect decreases with increasing cluster size. In small clusters it manifests itself by dimer evaporation of the odd-size clusters with n=3,5,11 and possibly n=7, while for all other cluster sizes dissociation by neutral monomer evaporation is observed. The clusters of size n=3, 9, 15, and 21 show particularly high dissociation energies and thus indicate electronic shell closures for n=2, 8, 14, and 20 atomic valence electrons. These results are compared with recent density functional theory calculations. The investigations on singly charged clusters are complemented by studies on doubly charged Cu-n(2+), n=15-25. These clusters decay by either neutral monomer evaporation, or, in the case of Cu-16(2+), by the emission of a trimer ion, Cu-3(+). Their dissociation energies show the behavior expected by analogy with the singly charged clusters with the same number of atomic valence electrons, n(e)=n-z, where z denotes the charge state. (C) 2001 American Institute of Physics.