Dynamics of valence hole excitations in adsorbates

Abstract

The valence photoemission spectra of NiCO, PdCO and PtCO are calculated by the ab‐initio Green’s function method using an extended basis set. The present ab initio many‐body approaches give a reasonably good description of the valence photoemission spectra of CO adsorbed on Ni, Pd and Pt metal surfaces. A detailed study of the dynamics of valence photoemission of CO adsorbed on different substrates is made. For the 1π level of NiCO and PtCO the quasi‐particle picture (Q.P.P.) breaks down, however, for PdCO the Q.P.P. is still valid. For the 4σ and 5σ levels of NiCO, the lowest energy state is the main line single hole (1h) state not the CT (charge transfer) 2h1p (two hole one particle) shakedown state. However, for PdCO and PtCO, the σ (π) to π* metal–ligand CT 2h 1p shakedown state of a non‐negligible intensity becomes the lowest energy state. The main line state is still 1h state and the Q.P.P. is valid. In PdCO and PtCO where the π bonding is weaker than in NiCO, the excitation from the σ metal orbital...