Nuclear spins, magnetic moments, and quadrupole moments of Cu isotopes from N=28 to N=46: Probes for core polarization effects

Measurements of the ground-state nuclear spins and magnetic and quadrupole moments of the copper isotopes from $^{61}\mathrm{Cu}$ up to $^{75}\mathrm{Cu}$ are reported. The experiments were performed at the CERN online isotope mass separator (ISOLDE) facility, using the technique of collinear laser spectroscopy. The trend in the magnetic moments between the $N=28$ and $N=50$ shell closures is reasonably reproduced by large-scale shell-model calculations starting from a $^{56}\mathrm{Ni}$ core. The quadrupole moments reveal a strong polarization of the underlying Ni core when the neutron shell is opened, which is, however, strongly reduced at $N=40$ due to the parity change between the $\mathit{pf}$ and $g$ orbits. No enhanced core polarization is seen beyond $N=40$. Deviations between measured and calculated moments are attributed to the softness of the $^{56}\mathrm{Ni}$ core and weakening of the $Z=28$ and $N=28$ shell gaps.