Angular Momentum

An understanding of angular momentum algebra is crucial for proper description of the properties and interactions of atoms. We therefore devote this chapter to a review of angular momentum. We begin with a quantum mechanical description of a particle of mass M confined to move on a plane circular ring of radius R. Such a description leads to the quantum mechanically allowable values of the energy and, of course, the angular momentum. In addition, this problem, which is often referred to as the rigid rotor, provides an introduction to a very important concept for the study of atomic structure—degeneracy.