Dipole and quadrupole moments of Cu73-78 as a test of the robustness of the Z=28 shell closure near Ni-78

Abstract

Nuclear spins and precise values of the magnetic dipole and electric quadrupole moments of the ground states of neutron-rich 73–78Cu isotopes were measured using the Collinear Resonance Ionization Spectroscopy (CRIS) experiment at the CERN On-Line Isotope Mass Separator (ISOLDE) facility. The nuclear moments of the less exotic 73,75Cu isotopes were remeasured with similar precision, yielding values that are consistent with earlier measurements. The moments of the odd-odd isotopes, and 78 29Cu (N =49) in particular, are used to investigate excitations of the assumed doubly magic 78Ni core through comparisons with large-scale shell-model calculations. Despite the narrowing of the Z =28 shell gap between N∼45 and N =50, the magicity of Z =28 and N =50 is restored toward 78Ni.This is due to weakened dynamical correlations, as clearly probed by the present moment measurements.status: publishe