Decay pathways and dissociation energies of copper clusters, Cu-n(+) (2 <=n <= 25), Cu-n(2+) (15 <= n <= 25)

The fragmentation pathways and dissociation energies of copper cluster cati ons, Cu-n(+) and Cu-n(2+), are determined by multiple-collision induced dis sociation. 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 ener gy than the average value of their even-size neighbors. The odd-even effect decreases with increasing cluster size. In small clusters it manifests its elf by dimer evaporation of the odd-size clusters with n=3,5,11 and possibl y n=7, while for all other cluster sizes dissociation by neutral monomer ev aporation is observed. The clusters of size n=3, 9, 15, and 21 show particu larly high dissociation energies and thus indicate electronic shell closure s for n=2, 8, 14, and 20 atomic valence electrons. These results are compar ed with recent density functional theory calculations. The investigations o n 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(+). Th eir dissociation energies show the behavior expected by analogy with the si ngly 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 Phy sics.