GIANT SATELLITE IN THE X-RAY PHOTOELECTRON-SPECTROSCOPY CORE-HOLE SPECTRA OF ADSORBATES

To investigate the dependence of ligand core-hole spectra on the electronic structure of the metal, we performed the ab initio 2h 2p/3h 2p configuration interaction (CI) calculation of the core-hole spectra of PdCO and Pd2 CO molecules, using an extended basis set. The main line is the one-hole state and takes a much larger intensity than for NiCO and NiN2 but still smaller than for free CO. As in the case of NiCO and NiN2, for both PdCO and Pd2 CO the pi-charge-transfer shakeup satellite of a small intensity is obtained. The most striking spectral feature of PdCO and Pd2 CO which differs from NiCO and NiN2 is the absence of the 5 eV giant sigma shakeup satellite in the carbon spectra of PdCO and Pd2 CO. For PdCO the corresponding oxygen satellite of small intensity is shifted toward the higher energy (around 8 eV). This oxygen satellite is missing in Pd2 CO. For the core-hole spectra of the CO/Pd(100) system which are not available, we expect satellite lines of small intensity around 10 eV. The absence and enhancement of the giant satellite in the core-hole spectra for the CO/Ni, N2/Ni, and CO/Pd systems are explained in terms of the different degree of the d-sigma-s hybrid and s-d promotion in the ground and ionized states.