COLLISION-INDUCED DISSOCIATION OF CR-N(+) (N=2-21) WITH XE - BOND-ENERGIES, DISSOCIATION PATHWAYS, AND STRUCTURES

The kinetic energy dependence of the collision-induced dissociation (CID) of Cr(n)+ (n = 2-21) with xenon is studied by using a guided ion beam mass spectrometer. Examination of the general dissociation behavior over a broad collision energy range shows that chromium cluster ions dissociate primarily by sequential atom loss with a few exceptions, most notably Cr5+. Bond energies of chromium cluster ions D(Cr(n-1)+-Cr) are determined from measurements of the CID thresholds. The cluster size dependence of chromium cluster bond energies shows that odd-sized clusters are more stable than even clusters for smaller clusters (n less-than-or-equal-to 9) and local maxima at n = 13, 14, and 20 for larger clusters. The even-odd alternation in the stability of small chromium clusters suggests that these cluster cations are bound mainly by the 4s electrons. The pattern of stability for the larger clusters, in particular, the observation that the 14- and 20-atom clusters are relatively stable, is consistent with clusters built around a dimer core.