Paper SS2-MoM11
Three-Dimensional Spatial Distribution of Desorbing N₂ and N₂O from Pd(211)

Monday, October 31, 2011, 11:40 am, Room 110

Spatial distributions of N₂ and N₂O desorbing from Pd(211), Pd(S)-[3(111)×(100)], in temperature programmed desorption (TPD) were measured after the N₂O dosing on the surface at 60 K. About one-third of N₂O molecules on the surface are found to desorb as N₂ by the decomposition with sharp concentration to 25° (θ = -25°) (100) side from the normal direction of (211) plane at 108 K in the parallel plane to [211] and [-111] directions at N₂O coverage of 1.0 ML. This indicates that N₂ desorbs without thermal equilibration by N₂O decomposition on Pd(211). From the preferential desorption direction (θ= -25°), the adsorption structure of N₂O just before the desorption is assigned as the bridge-structure at step-site, where O and terminal-N bonded with Pd at ontop (100) and 3fold hollow(111), respectively along the [-111] directions. On the other hand, the spatial distribution of desorbing N₂O obeyed cosine distribution directing the normal direction to the (211) plane, suggesting the existence of pre-desorption state on the surface.