Radiofrequency and Mössbauer Spectra of a Paramaghetic Ion in the Presence of Hyperfine Interactions and of Tunnel Effect

Abstract
The influence of a coherent tunnel effect on the magnetic hyperfine structure of a diluted paramagnetic ion, with an electronic ground state , is studied under the assumptions of zero longitudinal magnetic field and slow electronic relaxation. It is shown that the radiofrequency and Mössbauer spectra should be altered, with a change in the number and intensities of the lines. When the tunnelling parameter, , is large compared to the hyperfine structure, the magnetic hyperfine structure splitting should be strongly reduced and it should vanish for . Tunnelling effects have already been observed in EPR experiments on diluted in diamagnetic matrices. The cases of NMR with I=3/2 and of Mössbauer spectroscopy for a transition are considered.