Item

Abstract

The thermally induced decomposition of nitrous oxide on isolated Rh₅⁺ and Rh₅O⁺ clusters has been investigated using mid-infrared multiple photon dissociation spectroscopy. The presence of a single co-adsorbed oxygen atom is observed to have a profound effect on the cluster surface processes which ensue following infrared heating of the cluster. Exciting the infrared active N₂O bending transition in Rh₅N₂O⁺ results predominantly (≥ 85%) in molecular desorption of the N2O moiety whilst the same excitation in Rh₅ON₂O⁺ leads instead to N₂O dissociation on the cluster surface producing Rh₅O₂⁺ (≥ 85%). Calculations of the reaction pathway using density functional theory indicate that the change in branching ratio arises from a 0.4 eV greater binding energy of N₂O to Rh₅O⁺ compared with Rh₅⁺ taking the desorption threshold above the reaction barrier for the surface reaction channel whose energy is unchanged.