Free electron laser infrared action spectroscopy of nitrous oxide binding to platinum clusters, Pt_n(N₂O)

Infrared multiple-photon dissociation spectroscopy has been applied to study Pt_n(N₂O)⁺ (n = 1-8) clusters which represent entrance-channel complexes on the reactive potential energy surface for nitrous oxide decomposition on platinum. Comparison of spectra recorded in the spectral region 950 cm^-1 to 2400 cm^-1 with those simulated for energetically low-lying structures from density functional theory shows a clear preference for molecular binding via the terminal N atom, though evidence of O-binding is observed for some cluster sizes. Enhanced reactivity of Pt_n⁺n≥ 6 clusters towards N₂O is reflected in the calculated reactive potential energy surfaces and, uniquely in the size range studied, Pt₆(N₂O)⁺ proved impossible to form in significant number density even with cryogenic cooling of the cluster source. Infrared-driven N₂O decomposition, resulting in the formation of cluster oxides, Pt_nO⁺, is observed following vibrational excitation of several Pt_n(N₂O)⁺ complexes.