Electromagnetic moments of the odd-mass nickel isotopes $^{59-67}$Ni
nucl-ex
/ Authors
P. Müller, S. Kaufmann, T. Miyagi, J. Billowes, M. L. Bissell, K. Blaum, B. Cheal, R. F. Garcia Ruiz, W. Gins, C. Gorges
and 17 more authors
H. Heylen, A. Kanellakopoulos, S. Malbrunot-Ettenauer, R. Neugart, G. Neyens, W. Nörtershäuser, T. Ratajczyk, L. V. Rodríguez, R. Sánchez, S. Sailer, A. Schwenk, L. Wehner, C. Wraith, L. Xie, Z. Y. Xu, X. F. Yang, D. T. Yordanov
/ Abstract
The magnetic dipole and the spectroscopic quadrupole moments of the nuclear ground states in the odd-mass nickel isotopes $^{59-67}$Ni have been determined using collinear laser spectroscopy at the CERN-ISOLDE facility. They are compared to ab initio valence-space in-medium similarity renormalization group (VS-IMSRG) calculations including contributions of two-body currents as well as to shell-model calculations. The two-body-current contributions significantly improve the agreement with experimental data, reducing the mean-square deviation from the experimental moments by a factor of 3 to 5, depending on the employed interaction. For all interactions, the largest contributions are obtained for the $5/2^-$ ($7/2^-$) isotopes $^{65}$Ni ($^{55}$Ni), which is ascribed to the high angular momentum of the $f$ orbitals. Our results demonstrate that the inclusion of two-body-current contributions to the magnetic moment in an isotopic chain of complex nuclei can be handled by the VS-IMSRG and can outperform phenomenological shell-model calculations using effective $g$-factors in the nickel region.