Guided ion beam studies of the reactions of Fe_n⁺ (n=2-15) with D₂: Cluster-deuteride bond energies as a chemical probe of cluster structures

Abstract

The kinetic energy dependencies of the reactions of Fen+ (n=2-15) with D2 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 Fen+-D bond energies are compared to previously determined metal-metal bond energies, D0(Fen+-Fe). The bond energies of Fen+-D vary nonmonotonically with n, and parallel those for Fen+-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 Fen+ clusters. Arguments are presented to suggest that the thresholds measured for FenD2+ production correspond to barriers for chemisorbtion. © 1996 American Institute of Physics.