Selectivity of Auger decays to the local surface environment

The line shape of the Auger decay of adatoms is studied by a joint theoretical and experimental effort, the former within a DFT framework, and the latter with synchrotron radiation measurements. We investigate the KLV Auger deexcitation of Na on Al(111), a system with different adsorption 2;3p???p???? geometries. In particular, we study the ? 3 ? 3?R30 phase at 1=3 ML (monolayer) and the more complex ?2 ? 2? structure at 1=2 ML coverage. From the comparison between theory and experiment, we unambiguously determine features that allow for the determination of the adsorption environment from the adatom Auger spectrum.