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

摘要

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_nD~+ (n = 2-14) and Cr_nD_2~+ (n = 6-14). 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.