Core hole screening in chemisorption systems: Role of metal-adsorbate π→π* charge transfer

To clarify the physical picture of adsorbate ionization, the ligand core-hole spectra of a NiCO cluster used as a model of the CO/Ni(100) chemisorption system were obtained by large scale ab initio configuration interaction calculations. The computed C1s and O1s spectra are consistent with the experimental finding for the CO/Ni(100)c(2\ifmmode\times\else\texttimes\fi{}2) system. The results support the picture that the screening mechanism of the core hole on the ligand atoms is dominantly metal-ligand \ensuremath{\pi}\ensuremath{\rightarrow}\ensuremath{\pi}* charge transfer. \textcopyright{} 1996 The American Physical Society.