First-excited state $g$ factors in the stable, even Ge and Se isotopes

Abstract

Transient-field $g$-factor measurements in inverse kinematics were performed for the first-excited states of the stable, even isotopes of Ge and Se. The $g$ factors of ${}^{74}$Ge and ${}^{74}$Se were measured simultaneously using a cocktail beam, which eliminates most possible sources of systematic error in a relative $g$-factor measurement. The results are $g{(}^{74}\mathrm{Se})/g{(}^{74}\mathrm{Ge})=1.34(7)$, $g{(}^{70}\mathrm{Ge})/g{(}^{74}\mathrm{Ge})=1.16(15)$, $g{(}^{72}\mathrm{Ge})/g{(}^{74}\mathrm{Ge})=0.92(13)$, $g{(}^{76}\mathrm{Ge})/g{(}^{74}\mathrm{Ge})=0.88(5)$, $g{(}^{76}\mathrm{Se})/g{(}^{74}\mathrm{Se})=0.96(7)$, $g{(}^{78}\mathrm{Se})/g{(}^{74}\mathrm{Se})=0.82(5)$, $g{(}^{80}\mathrm{Se})/g{(}^{74}\mathrm{Se})=0.99(7)$ and $g{(}^{82}\mathrm{Se})/g{(}^{74}\mathrm{Se})=1.19(6)$. The measured $g$-factor ratios are in agreement with ratios from previous measurements, despite considerable variation in previous reported absolute values. The absolute values of the $g$ factors remain uncertain, however the Rutgers parametrization was used to set the transient-field strength and then compare the experimental $g$ factors with shell-model calculations based on the JUN45 and jj44b interactions. Modest agreement was found between experiment and theory for both interactions. The shell model calculations indicate that the $g(2_1^{+})$ values and trends are determined largely by the balance of the spin carried by orbital motion of the protons.

arXiv comment13 pages; 12 figures. Published as Phys. Rev. C 100, 044317 (2019). URL: https://link.aps.org/doi/10.1103/PhysRevC.100.044317

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