Theory of core-level photoemission correlation state spectra

Abstract

A theoretical framework is given for calculating satellite spectra (sometimes called ’’shakeup’’ or ’’monopole’’ spectra) that accompany core‐level photoemission peaks. Photoemission is regarded as a special case of optical excitation in an N‐electron system, and the dipole approximation (DA) is used to determine satellite intensities. relationships between the sudden approximation and DA results are noted. Configuration interaction (CI) in the final state is discussed. It is emphasized that the main core‐level peak and satellites do not really arise from one‐ and two‐electron excitations, respectively, but from qualitatively identical transitions. The importance of initial‐state CI in determining satellite intensities in molecular x‐ray photoelectron spectra is pointed out for the first time.