N2 adsorption onto the (2 × 2-O precovered Ru(0001) surface: a low-energy electron-diffraction study

The bond geometry of the mixed O + N2−(2 × 2) overlayer on Ru(0001) was determined by analyzing low-energy electron-diffraction intensity data. While the oxygen atoms sit in hcp sites, exhibiting a local adsorption geometry similar to that found in the pure O-(2 × 2) phase, the N2 molecules occupy on-top sites with their interatomic axis normal to the surface. The NN bond length is 1.12 ± 0.06 Å which is unchanged within the error bars if compared with the pure Ru(0001)-N2-(√3 × √3)R30° phase. The local reconstruction of the Ru(0001) surface in the mixed O + N2 phase is solely induced by oxygen adsorption.