Angular correlation in Auger Photoelectron Coincidence Spectroscopy from the Cu(111) surface

The feasibility of angle resolved APECS (Auger Photo-Electron Coincidence Spectroscopy) on solids is demonstrated with an experiment performed at the ALOISA beamline (ELETTRA, Trieste) on the L3M45M45 Auger transition of the Cu(111) surface. This beamline, with its multicoincidence detection system based on several individual electron analysers, was designed in order to perform such experiment with good efficiency. The correlation effects displayed by the measured angular distribution suggest inadequacy of the two step model that is usually adequate for non coincidence experiments performed at the same energy and on the same orbital.