GUIDED ION BEAM STUDIES OF THE REACTIONS OF FE-N(+)(N=2-15) WITH D-2 - CLUSTER-DEUTERIDE BOND ENERGIES AS A CHEMICAL PROBE OF CLUSTER STRUCTURES

摘要

The kinetic energy dependencies of the reactions of Fe-n(+) (n=2-15) with D-2 are studied in a guided ion beam mass spectrometer. The only products observed are FenD+ (n=2-15) and FenD2+ (n=9-15). All reactions are observed to exhibit thresholds, except for formation of Fe9D2+. Threshold analyses of the endothermic reactions lead to binding energies for the first deuterium atom to the cluster ions as a function of cluster size. The Fe-n(+)-D bond energies are compared to previously determined metal-metal bond energies, D-0(Fe-n(+)-Fe). The bond energies of Fe-n(+)-D vary nonmonotonically with n, and parallel those for Fe-n(+)-Fe except for notable differences at n=5, 8, 12, and 14. These trends are rationalized in terms of electronic and geometric structures for the Fe-n(+) clusters. Arguments are presented to suggest that the thresholds measured for FenD2+ production correspond to barriers for chemisorbtion. (C) 1996 American Institute of Physics. [References: 93]