Quasidegenerate perturbation theory configuration interaction calculations of the core and valence photoelectron spectra of Ne and Ar

Abstract

Quasidegenerate perturbation theory within the configuration interaction approach (QDPT CI) is applied to the calculation of photoelectron spectra of Ne and Ar, employing the sudden approximation for the calculation of the intensities. This approach proves to be able to take into account properly the dynamical and nondynamical correlation effects for both the valence and core ionizations, provided that static relaxation effects are explicitly taken into account through the use of SCF relaxed orbitals for the core processes. The importance of the choice of the zero-order space, which must comprise the strongly interacting configurations, is discussed and good agreement with the experimental data is obtained also employing zero-order spaces of limited dimension, the possible remaining discrepancies being due to limitations of the basis set employed or of the approach used for the calculation of the intensities. The method proves therefore to be adequate for a quantitative description of the entire photoionization spectra of Ne and Ar, reproducing both the energies and the intensities of the rich satellite structures.