Investigation of nuclear charge radii of neutron-rich zinc isotopes crossing N=50

The nuclear shell model is a well-established framework that has consistently demonstrated its ability to reproduce and predict nuclear properties across a wide range of nuclei. Over many years, it has proven to be a powerful tool for describing and forecasting the behavior of nuclei in multiple regions of the nuclear chart, especially its prediction of magic numbers. Magic numbers (2, 8, 20, 28, 50, ...) are the amount of either protons or neutrons that correspond to a completely filled shell followed by a large energy gap. However, from studying exotic nuclei it is found that these magic numbers change when moving far away from stability. In these radioactive nuclei, the energy levels of single-particle orbits begin to shift due to nucleon-nucleon interactions, a phenomenon known as shell evolution. To gain more knowledge about the nuclear structure and nuclear properties in regions far from stability, it is essential to study exotic nuclei. For this reason, nuclear properties of neutron-rich zinc isotopes have been investigated, with a focus on nuclear charge radii crossing the magic gap N=50, and the determination of the spin of $^{81}$Zn. The technique used to study the neutron-rich zinc isotopes is collinear resonance ionization spectroscopy, performed at the CRIS beam-line in ISOLDE, CERN. From these measurements, hyperfine spectra are obtained from which various nuclear properties are extracted such as spin, magnetic dipole moment, electric quadrupole moment, and mean square charge radii. A detailed overview is given of the analysis of hyperfine spectra which are measured for isotopes of $^{64}$Zn up to $^{82}$Zn. Prior to this work, neutron-rich zinc isotopes up to $^{80}$Zn have been investigated by the COLLAPS group. In addition to that, the spin of $^{81}$Zn is experimentally determined for the first time: $I = 5/2$. This finding indicates that no level inversion takes place for the ground state of $^{81}$Zn. Furthermore, the nuclear magnetic and quadrupole moment for this isotope are extracted, with the result of a possible configuration mixing. Finally, the nuclear mean square charge radii are obtained which are in a good agreement with the findings of COLLAPS. A strong kink is observed when crossing N=50, proving a strong shell closure.