Guided ion beam studies of the reactions of Cr-n(+) (n=2-14) with D-2: cluster-deuteride bond energies as a chemical probe of cluster electronic structure

The kinetic energy dependencies of the reactions of chromium cluster cation s, Cr-n(+) (n = 2-14), with D-2 are studied in a guided ion beam mass spect rometer. The observed products are CrnD+ (n = 2-14) and CrnD2+ (n = 614). A ll reactions are observed to exhibit thresholds, except for formation of th e dideuteride product for Cr-n(+) (n = 6-8). Threshold analyses of the endo thermic reactions reveal binding energies for the first deuterium atom to t he cluster ions as a function of cluster size. The Cr-n(+)-D bond energies are compared to previously determined metal-metal bond energies, D-0(Cr-n()-Cr). The bond energies of Cr-n(+)-D exhibit odd-even oscillations with n that parallel those of Cr-n(+)-Cr. These trends support our earlier suggest ion that bonding in Cr-n(+) clusters, at least for n = 2-11, are governed b y electronic factors. (C) 2000 Elsevier Science B.V. All rights reserved.