Guided ion beam studies of the reactions of Crn+ (n=2-14) with D2:: cluster-deuteride bond energies as a chemical probe of cluster electronic structure

The kinetic energy dependencies of the reactions of chromium cluster cations, Cr(n)(+) (n = 2-14), with D(2) are studied in a guided ion beam mass spectrometer. The observed products are Cr(n)D(+) (n = 2-14) and Cr(n)D(2)(+) (n = 614). All reactions are observed to exhibit thresholds, except for formation of the dideuteride product for Cr(n)(+) (n = 6-8). Threshold analyses of the endothermic reactions reveal binding energies for the first deuterium atom to the 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 suggestion that bonding in Cr(n)(+) clusters, at least for n = 2-11, are governed by electronic factors. (C) 2000 Elsevier Science B.V. All rights reserved.