Construction of the energy matrix for complex atoms Part IV: Excitation of one electron from a closed shell into an open shell

This work is a continuation of the previous series related to the construction of the energy matrix for complex atoms. The effects of the second-order configuration interaction perturbations on the energy-level structure of nlN , nlNn₁l₁^N₁ and nlNn₁l₁^N₁n₂l₂ configurations were studied. In this paper we consider one-electron core excitations for and between the configurations under study. This work combined with Part II and III is a complete description of an electrostatic interaction. In Part I we presented a method which allows to analyse complex electronic systems. They constitute the basis for the design of an efficient computer program package allowing large scale calculations which provide accurate wave functions.