Giant satellite in the x-ray photoelectron spectroscopy core-hole spectra of adsorbates

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Abstract
To investigate the dependence of ligand core‐hole spectra on the electronic structure of the metal, we performed the ab initio 2h2p/3h2p configuration interaction (CI) calculation of the core‐hole spectra of PdCO and Pd2CO 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 Pd2CO the π charge‐transfer shakeup satellite of a small intensity is obtained. The most striking spectral feature of PdCO and Pd2CO which differs from NiCO and NiN2 is the absence of the 5 eV giant σ shakeup satellite in the carbon spectra of PdCO and Pd2CO. For PdCO the corresponding oxygen satellite of small intensity is shifted toward the higher energy (around 8 eV). This oxygen satellite is missing in Pd2CO. 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 dσ‐s hybrid and s‐d promotion in the ground and ionized states.