t-Butyl nitrite adsorbed on Ag(1 1 1): thermally activated structure changes

Dosed on Ag(1 1 1) at 80 K, t-butyl nitrite ((CH3)3CONO, TBN) adsorbs and desorbs without dissociation but during subsequent thermal activation, reflection absorption infrared spectra, reveal significant structural changes within both the multilayer and monolayer. Vibrational peaks of TBN dosed at 80 K and of matrix-isolated TBN lie within 15 cm−1 of each other. Reflecting local ordering within the multilayer upon annealing to 110 K, the vibrational peaks sharpen and shift slightly. As the annealing temperature increases further, the NO stretch to C–H stretch intensity ratio drops dramatically revealing alignment changes with respect to the silver surface in both multilayer and monolayer. The relative intensities of other modes also change and, using symmetry assignments, we conclude that the ensemble average angle between the CONO plane of TBN and the Ag(1 1 1) surface decreases as the annealing temperature increases. The potential impact of such alignment changes on ejection of NO during photodissociation of TBN is discussed.