12. Angular momentum

The quantum mechanics of angular momentum is fascinating. It is also very basic to much of quantum mechanics. It is a model for dealing with other systems of particles

In chapter 5.4, it was already mentioned that angular
momentum of particles comes in two basic kinds. Orbital angular
momentum is a result of the angular motion of particles, while spin is
built-in

angular momentum of the particles.

Orbital angular momentum is usually indicated by and spin
angular momentum by . A system of particles will normally
involve both orbital and spin angular momentum. The combined angular
momentum is typically indicated by

However, this chapter will use as a generic name for any angular momentum. So in this chapter can indicate orbital angular momentum, spin angular momentum, or any combination of the two.

- 12.1 Introduction
- 12.2 The fundamental commutation relations
- 12.3 Ladders
- 12.4 Possible values of angular momentum
- 12.5 A warning about angular momentum
- 12.6 Triplet and singlet states
- 12.7 Clebsch-Gordan coefficients
- 12.8 Some important results
- 12.9 Momentum of partially filled shells
- 12.10 Pauli spin matrices
- 12.11 General spin matrices
- 12.12 The Relativistic Dirac Equation