COLLISION-INDUCED DISSOCIATION OF NIN+ (N=2-18) WITH XE - BOND-ENERGIES, GEOMETRICAL STRUCTURES, AND DISSOCIATION PATHWAYS

The kinetic energy dependence of the collision-induced dissociation (CID) of Ni(n)+ (n = 2-18) with xenon is studied by using a guided ion beam mass spectrometer. Bond energies of nickel cluster ions, D0(Nin-1+-Ni), are determined from measurements of the CID thresholds. Bond energies for neutral nickel clusters, D0(Nin-1-Ni), are derived by combining these ionic bond energies with literature values of ionization energies for Ni(n). Both D0(Nin-1+-Ni) and D0(Nin-1-Ni) are found to increase nonmonotonically as a function of cluster size, with local maxima at n = 3, 7, and 13 for ionic clusters and at n = 6 and 13 for neutral clusters. Examination of the cluster size dependence of nickel cluster bond energies leads to speculations on the likely cluster geometric structures. Examination of the general dissociation behavior over a broad collision energy range shows that nickel cluster ions dissociate primarily by sequential atom loss, although exceptions are noted.