ANGULAR-RESOLVED AUTOIONIZATION STUDY OF CO ON NI(110) - EXPERIMENT AND THEORY

Angular-resolved autoionization spectra after core-to-bound excitation of CO absorbed on Ni(110) in the (2 X 1)p2mg structure are presented. The experimental autoionization spectra are compared with calculated spectra for the model system Ni-CO by application of the many-body Gre en's-function technique using self-consistent-field results-molecular orbital-complete neglect of differential overlap one-particle wave fun ctions. In order to supplement the semiempirical approach we furthermo re carried out ab initio calculations of the autoionization rates. The angular dependences of the autoionization lines are explicitly calcul ated. The core-valence-valence Auger spectrum of Ni-CO after C1s and O 1s excitation has been calculated by the particle-particle Green's-fun ction method with subsequent calculation of the radiationless Auger ra tes. The combination of the theoretical approaches and the information gained from the angular electron distribution allows one to assign th e spectra obtained after core-to-bound and core-to-continuum excitatio n within the framework of molecular-orbital theory.