LS-Coupling

Abstract

In the LS-coupling scheme, we analyse multielectron atoms by first applying the central-field approximation, and thereafter treating the multitude of angular momentum interactions as perturbations, in decreasing order of magnitude. LS-coupling is the specific limiting case of this one where we assume that we can first apply solely the angular contribution of the electrostatic interaction between the electrons as a perturbation, and only after that the spin–orbit interactions. Here, we extend the previous treatment to more complex situations, put the theory on a more rigorous theoretical footing, and go into more detail. Initially, we focus on LS-coupling atomic terms, while temporarily ignoring spin–orbit couplings, and we make estimates of the term energies. After that, we add the fine-structure to the treatment, and eventually, we explore the functional form of the LS-coupling states.