Regensburg 2013 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 78: Surface Dynamics I
O 78.1: Vortrag
Donnerstag, 14. März 2013, 16:00–16:15, H42
"Pick-up" mechanism in the scattering of hyperthermal N atoms off N-covered Ag(111) — •María Blanco-Rey1, Estíbaliz Díaz1, Gisela Bocan2, Ludovic Martin-Gondre1,3,4, Ricardo Díez-Muiño1,3, Maite Alducin1,3, and J. Iñaki Juaristi1,3,5 — 1Donostia International Physics Center, 20018 Donostia-San Sebastián, Spain — 2CONICET and CNEA, 8400 S.C. de Bariloche, Argentina — 3Centro de Física de Materiales, Centro Mixto CSIC-UPV/EHU, 20018 Donostia — 4Institut des Sciences Moléculaires, CNRS UMR 5255 / Université Bordeaux I, 33405 Talence, France — 5Dept. de Física de Materiales, Facultad de Químicas UPV/EHU, Ap. 1072, 20018 Donostia
An ab-initio 3D potential energy surface (PES) and classic molecular dynamics (MD) are used to study the reflection and adsorption dynamics of N atoms on N-covered Ag(111). We find that the surface N species modify the PES dramatically, adding corrugation and an attractive well above the adsorbed N, but MD shows that the scattered N angular distributions change little upon N adsorption, in agreement with molecular beams experiments. However, this level of theory fails to reproduce the experimental final-to-initial average energy ratios, ⟨ Ef ⟩/ ⟨ Ei ⟩, at grazing angles. From a close examination of N sticking, we infer that gas N is likely to "pick-up" adsorbed N species to form N2. This mechanism is active mainly at low energies. With this in mind, the experimental energy ratios are explained by the surface being partially cleaned as the experiment is being conducted. Simulations with a 6D PES support the "pick-up" process efficiency.