Angle-Dependent Changes of Auger Line Shapes from Adsorbed Molecules

Strong polar-angle dependence has been observed in KVV-Auger spectra of adsorbed molecules. These angular effects are caused by the anisotropy of the Auger matrix element and can be explained by simple symmetry arguments. It is shown with the example CO on Ni(100) that molecular Auger spectra can be largely understood with use of nothing but the present angular results and experimental one-electron binding energies. Information about the adsorbate orientation as well as about the screening mechanism can also be obtained.