Collinear Laser Spectroscopy of Potassium : Nuclear Charge Radii beyond N=28

Nuclear ground-state properties, such as spin, charge radius, and magnetic dipole and electric quadrupole moments are important quantities to describe the nucleus. The comparison of experimental data to shell-model calculations gives insight in the underlying nuclear structure and composition of ground-state wave functions. Spins and charge radii can also be used to test the predictions of state-of-the-art microscopic models. This work contributes to these studies providing new measurements in the region of the nuclear chart around the magic proton number Z=20. The data have been obtained at the collinear laser spectroscopy setup COLLAPS located at the radioactive-ion-beam facility ISOLDE at CERN. Using bunched-beam laser spectroscopy hyper fine structure spectra of the potassium isotopes with mass number A=48-51 could be recorded for the first time. Ground-state spins and isotope shifts could be deduced for 48-51K contributing to the evolution of the proton d3/2 orbital beyond the shell closure at the magic neutron number N=28. Charge radii deduced from isotope shifts provide information towards the systematics of the charge radii in the calcium region beyond the N=28 shell closure. While theoretical calculations predict the correct spins, the charge radii still provide a challenge even to the newest relativistic mean-field and coupled cluster models