Magnetic moments of g_9/2 isomeric states around ⁶⁸Ni

Magnetic moments of excited nuclear states provide sensitive probes to the contributions of the single-particle configurations to the nuclear wave functions. This is especially true close to shell closures where the wave functions are expected to be quite pure. A peculiar case is that of ⁶⁸Ni, which lies at the N=40 sub-shell closure between the fp shell and the g_9/2 orbital. It exhibits some signatures of doubly-magic nuclei, such as a low B(E2;2⁺₁→0⁺_g.s.) value and a 0⁺ first excited state, however, mass measurements show no sign of magicity in the two-neutron separation energies. Further insight into the nuclear structure of this region could be obtained through measurements of magnetic moments of g_9/2 isomeric states. An experiment was performed at the NSCL facility of MSU to determine the magnetic moments of isomeric states in ^67,69,70Ni. The nuclei of interest were produced via the fragmentation of a 130-MeV/u ⁷⁶Ge beam and were implanted at the center of a dedicated setup, consisting of a plastic scintillator, 4 SeGa HPGe detectors, and an electromagnet. The Time-Dependent Perturbed Angular Distribution method was utilized to observe the Larmor precession of the nuclear spins, oriented in the fragmentation reaction, and to extract the magnetic moments of the isomeric states. The obtained experimental results will be presented and compared to modern shell-model calculations using the LNPS interaction.