Guided ion-beam studies of the kinetic-energy-dependent reactions of Co-n(+) (n=2-16) with D-2: Cobalt cluster-deuteride bond energies - art. no. 194320

摘要

The kinetic-energy-dependent cross sections for the reactions of Co-n(+) (n=2-16) with D-2 are measured as a function of kinetic energy over a range of 0-8 eV in a guided ion-beam tandem mass spectrometer. The observed products are ConD+ for all clusters and ConD2+ for n = 4,5,9-16. 2 Reactions for the formation of ConD+ (n=2-16) and Co9D2+ are observed to exhibit thresholds, 2 whereas cross sections for the formation of ConD2+ (n=4,5,10-16) exhibit exothermic reaction 2 behavior. The Co-n(+)-D bond energies as a function of cluster size are derived from the threshold analysis of the kinetic-energy dependence of the endothermic reactions and are compared to previously determined metal-metal bond energies, D-0(Co-n(+)-Co). The bond energies of Co-n(+)-D generally increase as the cluster size increases, and roughly parallel those for Co-n(+)-Co for clusters n >= 4. These trends are explained in terms of electronic and geometric structures for the Co-n(+) clusters. The bond energies of Co-n(+)-D for larger clusters (n >= 10) are found to be very close to the value for chemisorption of atomic hydrogen on bulk-phase cobalt. The rate constants for D-2 chemisorption on the cationic clusters are compared with the results from previous work on cationic and neutral cobalt clusters. (c) 2005 American Institute of Physics.