Determine the origin of the anomalous $^{119m}$Ag nuclear $g$-factor jump

Determine whether the abrupt jump in the nuclear $g$-factor for the spin-$7/2$ state at neutron number $N=72$ in $^{119m}$Ag is a genuine nuclear-structure effect or an artifact of the analysis of the reported hyperfine $A$-factors.

Background

The paper extracts magnetic dipole moments and hydrogen-like Bohr–Weisskopf nuclear magnetization parameters for radioactive Ag isotopes by combining measured hyperfine factors with high-accuracy electronic-structure calculations. For most neutron-rich isotopes, the extracted values rely on solving a two-equation system involving the ground-state and excited-state hyperfine factors.

The analysis reveals an unexpected discontinuity at the isomeric state 119m^{119m}Ag. The authors cannot distinguish between a physical change in nuclear structure and an experimental or data-analysis artifact, and they explicitly call for a remeasurement of this isotope. Resolving this issue is important for determining whether the inferred magnetic moment and magnetization-distribution parameter are reliable nuclear observables.

References

We observe no statistically significant deviation in the magnetic dipole moments measured by Ferrer et al. and de Groote et al. for the two reference isotopes. Note that an additional error is introduced when ${107}$Ag is used as a reference due to the uncertainty in the differential HFA (${107}\Delta {109}$). However, there remains a disagreement on the magnetic dipole moment of ${101}$Ag ($N=54$), which was measured by Ferrer et al. in the $5s\, 2S_{1/2}$ atomic state and by Dinger et al. in the $4d95s2\, 2D_{5/2}$ state. Likely, the disagreement is due to the effect of the HFA between ${101}$Ag and the reference isotopes ${107}$Ag and ${109}$Ag, which has a significant contribution in $5s\, 2S_{1/2}$ but a negligible one in $4d95s2\, 2D_{5/2}$. For example, an HFA of ${107}\Delta{101}\approx$~${109}\Delta{101}\approx -1.8\%$ would bring the $g$-factor of ${101}$Ag extracted from data by Ferrer et al. and Dinger et al. into agreement. However, due to the low precision in the data by Ferrer et al., it is not possible to determine the values for ${107}\Delta{101}$ and ${109}\Delta{101}$ with an uncertainty of less than 100\%. As a result, there is a need for high-precision laser spectroscopy of ${97-105}$Ag in the atomic $5s\, 2S_{1/2}$ and $5p\, 2P_{1/2}$ or $5p\, 2P_{3/2}$ levels to determine the HFA for these isotopes.

— Nuclear moments, charge radii, and magnetization distribution parameters of Ag isotopes from laser spectroscopy and \textit{ab initio} electronic-structure calculations  (2609.40130 - Skripnikov et al., 30 Sep 2026) in Section 2, subsection “Nuclear magnetic dipole moments of radioactive isotopes”