Nitrogen Scattering at Ru(0001) Surfaces

Results on the scattering of hyperthermal N2 molecules from bare and N-covered Ru(0001) surfaces are presented. These are compared with Ar scattering from the same surfaces as a reference non-reactive system. In the case of bare Ru(0001) the measured angular distributions are consistent with scattering from an atomically smooth surface after interaction with a repulsive potential energy surface. Broadening of the N2 angular intensity distribution at high incident energy, which was observed in molecular beam studies, is not apparent in our measurements. This is attributed to the broadening effect being the result of a transient trapping process that is confined to a relatively narrow incident energy range. The presence of N-adatoms on the surface results in atomic-scale surface roughening and blocking of dissociation pathways. Formation of N2 molecules as a result of abstraction of N-adatoms by incident N-atoms in an Eley–Rideal-type reaction is considered. Support for such a process is derived from comparison of the trends in the angular energy distributions of N2 and Ar.