The thermochemistry of adsorbates on transition metal cluster ions: relationship to bulk-phase properties

In previous work, guided ion beam tandem mass spectrometry has been used to study the reactions of the cluster cations of several transition metals (V, Cr, Fe and Ni) with D2, O2, CO2 and CD4. By examining the kinetic energy dependence of these reactions and interpreting thresholds observed for various reactions, bond energies for D, O, C, CD, CD2 and CD3 can be obtained. The results of these studies are reviewed with an emphasis on the relationship between the thermochemistry obtained from this work with that for adsorbates on bulk-phase metal surfaces. It is found that in cases where quantitative comparison can be made, for example D and O atoms, modest sized clusters bind these species to approximately the same extent as the bulk-phase surface of the same metal. As there is little information available for the molecular fragments investigated here, the cluster bond energies provide some of the first experimental values for such adsorbates on surfaces.