EPR: Principles

Abstract

The basic methodology and development of the spin Hamiltonian method as well as the terminology and sym-bols used in EPR developed out of atomic spectroscopy. Therefore it is useful to review how atomic spectroscopy of atoms and ions dealt with the Zeeman effect, which is the effect of a magnetic field on atomic spectra. This is all covered in the classic work by Herzberg [1]. Angular Momentum All magnetic properties of materials have their origin in angular momentum of electrons, nuclei, and molecules. Since the quantum mechanics of angular momentum is identical for all species, we will review the important el-ements of the quantum mechanics for the nuclear spin. The three operators of nuclear spin about the three coor-dinates arê I x I y , an I z . These operators are in units of h --. From the commutation properties of these three operators, it can be shown that the nuclear spin func-tions are eigenfunctions of the total angular momen-tum operator I 2