The role of jj coupling on the energy levels of heavy atoms

Abstract

The study of atomic spectroscopy has a profound relationship with quantum mechanics and its comprehension. Since Bohr’s success with a theory for the atom, it has been established that spectrum lines originate from transitions between different states. Moreover, the analysis of complex spectra reveals that there are groups of spectral lines that compose what is called a multiplet. To rationalize the multiplet structure, we need models to characterize and label the quantum states. The characterization of the atomic states is a common subject in classes of physical chemistry and inorganic chemistry, and there are basically two approaches to infer and label the energy states: (i) the LS coupling scheme and (ii) the jj coupling scheme. Usually, only the LS coupling is presented, and this ends up omitting its underlying assumptions. Here, we present a survey of both approaches, highlighting their premises and their adequacy towards different groups of the periodic table, ions, and excited states configurations. We show that by using benchmark data together with the Landé interval rule, the appropriate use of the jj coupling to understand the atomic spectra of heavier atoms is easily conveyed.

Keywords

• spin-orbit coupling
• LS coupling
• jj coupling
• spectroscopic terms
• atomic energy levels