J. Phys. I France
Volume 6, Numéro 1, January 1996
Page(s) 137 - 147
DOI: 10.1051/jp1:1996133
J. Phys. I France 6 (1996) 137-147

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

Françoise Hartmann-Boutron

Laboratoire de Spectrométrie Physique UJF-CNRS, UA 08, Université J. Fourier - Grenoble I, B.P. 87, 38402 Saint Martin d'Hères Cedex, France

(Received 13 July 1995, revised in final form and accepted 2 October 1995)

The influence of a coherent tunnel effect on the magnetic hyperfine structure of a diluted paramagnetic ion, with an electronic ground state $\vert S_z=\pm S>(S>\frac 12)$, 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, $\Gamma$, is large compared to the hyperfine structure, the magnetic hyperfine structure splitting should be strongly reduced and it should vanish for $\Gamma \rightarrow \infty$. Tunnelling effects have already been observed in EPR experiments on ${\rm Tb}^{3+}$ diluted in diamagnetic matrices. The cases of NMR with I=3/2 and of Mössbauer spectroscopy for a transition $I_{\rm e}=3/2\rightarrow I_{\rm g}=1/2$ are considered.

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