General cases of the pseudoquadrupole interaction in¹⁶⁹Tm

Abstract

Clauser and Mössbauer [1] showed that the second order (in perturbation theory) magnetic hyperfine interaction, the so called “pseudoquadrupole inter-action”, in the¹⁶⁹Tm Mössbauer effect can produce apparent isomer shifts. While they assumed two isolated singlets and simplified the coupling, we will show that the second order magnetic hyperfine coupling can be observed in general for any kind of crystalline electric field (CEF) wavefunctions, and that the coupling between many states must often be considered in calculating it. Furthermore since the first order magnetic coupling of the excited CEF states is important, the interaction is best accounted for by diagonalization of the full magnetic hyperfine and CEF Hamiltonian. Examples of the effects that may occur are presented.