Book contents
- Frontmatter
- Contents
- Preface
- 1 Introduction: the need for a quantum theory
- 2 Experimental foundations of quantum theory
- 3 Waves and particles
- 4 Schrödinger picture, Heisenberg picture and probabilistic aspects
- 5 Integrating the equations of motion
- 6 Elementary applications: one-dimensional problems
- 7 Elementary applications: multi-dimensional problems
- 8 Coherent states and related formalism
- 9 Introduction to spin
- 10 Symmetries in quantum mechanics
- 11 Approximation methods
- 12 Modern pictures of quantum mechanics
- 13 Formulations of quantum mechanics and their physical implications
- 14 Exam problems
- 15 Definitions of geometric concepts
- References
- Index
9 - Introduction to spin
Published online by Cambridge University Press: 05 November 2014
- Frontmatter
- Contents
- Preface
- 1 Introduction: the need for a quantum theory
- 2 Experimental foundations of quantum theory
- 3 Waves and particles
- 4 Schrödinger picture, Heisenberg picture and probabilistic aspects
- 5 Integrating the equations of motion
- 6 Elementary applications: one-dimensional problems
- 7 Elementary applications: multi-dimensional problems
- 8 Coherent states and related formalism
- 9 Introduction to spin
- 10 Symmetries in quantum mechanics
- 11 Approximation methods
- 12 Modern pictures of quantum mechanics
- 13 Formulations of quantum mechanics and their physical implications
- 14 Exam problems
- 15 Definitions of geometric concepts
- References
- Index
Summary
First, the experimental foundations for the existence of a new dynamical variable, the spin of particles, are presented. The Pauli equation is then derived in detail, two applications are given and the energy levels of a particle with spin in a constant magnetic field are studied. This is the analysis of Landau levels, which can be performed by using the known results on the spectrum of harmonic oscillators. In this chapter we also study in detail the addition of orbital angular momentum and spin, as well as the spin–orbit interaction with the resulting Thomas precession.
Stern-Gerlach experiment and electron spin
The hypothesis that the electron has an intrinsic magnetic moment and an angular momentum, in short a spin, was first suggested in Uhlenbeck and Goudsmit (1926). They noticed, even before the discovery of quantum mechanics, that a complete description of spectra was not possible unless a magnetic moment and a mechanical moment were ascribed to the electron, and hence the concept of an electron as a point charge was insufficient. First, let us therefore try to understand how a magnetic moment can be associated to an atomic system. For this purpose, consider for simplicity the Bohr model of an hydrogen atom, where the electron moves along a circular orbit and rotates with orbital angular momentum L.
- Type
- Chapter
- Information
- Advanced Concepts in Quantum Mechanics , pp. 195 - 213Publisher: Cambridge University PressPrint publication year: 2014