# $g$ Factor of the $^{99}\mathrm{Zr}$ ($7/{2}^{+}$) Isomer: Monopole Evolution in the Shape-Coexisting Region

Abstract : The gyromagnetic factor of the low-lying E=251.96(9)  keV isomeric state of the nucleus Zr99 was measured using the time-dependent perturbed angular distribution technique. This level is assigned a spin and parity of Jπ=7/2+, with a half-life of T1/2=336(5)  ns. The isomer was produced and spin aligned via the abrasion-fission of a U238 primary beam at RIKEN RIBF. A magnetic moment |μ|=2.31(14)μN was deduced showing that this isomer is not single particle in nature. A comparison of the experimental values with interacting boson-fermion model IBFM-1 results shows that this state is strongly mixed with a main νd5/2 composition. Furthermore, it was found that monopole single-particle evolution changes significantly with the appearance of collective modes, likely due to type-II shell evolution.
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https://hal.archives-ouvertes.fr/hal-02518019
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F. Boulay, G.S. Simpson, Y. Ichikawa, S. Kisyov, D. Bucurescu, et al.. $g$ Factor of the $^{99}\mathrm{Zr}$ ($7/{2}^{+}$) Isomer: Monopole Evolution in the Shape-Coexisting Region. Phys.Rev.Lett., 2020, 124 (11), pp.112501. ⟨10.1103/PhysRevLett.124.112501⟩. ⟨hal-02518019⟩

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