Construction of the energy matrix for complex atoms Part III: Excitation of two equivalent electrons from a closed shell into an open shell or an empty shell

Abstract

The effects of the second-order configuration interaction perturbations on the energy-level structure of nl N , $$nl^N n_1 l_1^{N_1 }$$ and $$nl^N n_1 l_1^{N_1 } n_2 l_2$$ configurations have been studied. In the previous works (see Part I and II) we presented a method, which allows to analyse complex electronic systems composed of configurations including up to four open shells and the formulae for the first-order electrostatic interaction between sophisticated configurations. In the present paper we consider two-electron core excitations for and between the configurations under study. They constitute the basis for the design of an efficient computer program package allowing large-scale calculations providing accurate wave functions.