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arXiv · 1812.03921

Theoretical predictions for the magnetic dipole moment of $^{229m}$Th

Nikolay Minkov·Adriana Pálffy
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Abstract

A recent laser spectroscopy experiment [J. Thielking et al., Nature (London) 556, 321 (2018)] has determined for the first time the magnetic dipole moment of the 7.8 eV isomeric state $^{229m}$Th. The measured value differs by a factor of approximately 5 from previous nuclear theory predictions based on the Nilsson model, raising questions about our understanding of the underlying nuclear structure. Here, we present a new theoretical prediction based on a nuclear model with coupled collective quadrupole-octupole and single-particle motions. Our calculations yield an isomer magnetic dipole moment of $μ_{ IS}= -0.35μ_N$ in surprisingly good agreement with the experimentally determined value of $-0.37(6)μ_N$, while overestimating the ground state dipole moment by a factor 1.4. The model provides further information on the states' parity mixing, the role and strength of the Coriolis mixing and the most probable value of the gyromagnetic ratio $g_R$ and its consequences for the transition probability $B(M1)$.

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Nikolay Minkov, Adriana Pálffy. 2018-12-10. Theoretical predictions for the magnetic dipole moment of $^{229m}$Th. https://doi.org/10.1103/physrevlett.122.162502

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