Hyperfine Interactions

Abstract

In Chap.{\thinspace}2, for the sake of simplicity, we dealt with transitions between unperturbed energy levels of ``bare'' nuclei with the mean transition energy E0. In reality, however, nuclei are exposed to electric and magnetic fields created by the electrons of the Mössbauer atom itself and by other atoms in the neighborhood. These fields generally interact with the electric charge distribution and the magnetic dipole moment of the Mössbauer nucleus and perturb its nuclear energy states. The perturbation, called nuclear hyperfine interaction, may be such that it shifts the nuclear energy levels, as is the case in the electric monopole interaction (e0), or such that it splits degenerate states, as afforded by the electric quadrupole interaction (e2) and the magnetic dipole interaction (m1). Only these three kinds of interaction must be considered in practical Mössbauer spectroscopy.