Knowledge Bank

“Over the past decade considerable attention has been given to the application of the linear of configuration interaction of the analysis of the energy levels of systems of equivalent electrons. The linear theory has sought to augment the usual Hamiltonian for an N electron system with additional two-body scalar interactions. By choosing the correct scalar interactions it has been found possible to include, to second-order, all the electrostatic interaction with configurations having two electrons excited from the $lN$ configuration. Using perturbation theory it been found possible to derive explicitly the form of the scalar interaction. Effective three-body interactions are introduced to account for the perturbations due to one electron excitations. The physical significance of the parameters associated with the linear theory is clarified. The effect of configuration interaction on spin-orbit coupling constants and crystal field parameters will also be discussed.”