First Experimental Determination of an Adsorption Site Using Multiple Wave Number Photoelectron Diffraction Patterns

* M. Zharnikov, M. Weinelt, P. Zebisch, M. Stichler, and H.-P. Steinrück

Angular distributions of S 2p_3/2 photoelectrons were measured for Ni(111)-p(2 x 2)S at seven kinetic energies between 130 and 322.5 eV. Using these data, the real space structure around the emitter is reconstructed using the multiple wave number phased-sum algorithm. The reconstructed images allow the unequivocal identification of the fcc adsorption site, with a distance from the S atoms to the top Ni layer of 1.6 Å. This is, to our knowledge, the first example wherein the multiple wave number phased-sum method has successfully been applied to determine an adsorption site from experimental data.