Structure of potassium isotopes studied with collinear laser spectroscopy

Hyperfine spectra of 48-51K (Z = 19) isotopes were measured at ISOLDE (CERN) for the first time, providing nuclear structure information when filling the ν2p3/2 orbit up to N = 32. The experiment was performed at the high-resolution collinear laser spectroscopy set-up (COLLAPS) with an improved highly efficient optical detection system. The analysis yielded the nuclear spin, magnetic moments and differences in mean square charge radii for isotopes between N = 19 and N = 32. The determination of the nuclear spin and magnetic moments of the neutron-rich isotopes, together with the isomeric shift in 38K were the main topics of this thesis. The measured ground-state spins of 49K (I = 1/2) and 51K (I = 3/2) shed light on the evolution of the 1/2+ and 3/2+ states beyond N = 28. The observed re-inversion of these levels points to the role of the monopole interaction in the evolution of the shell structure. In addition, magnetic moments probe the configuration and purity of the ground-state wave function. A considerable mixing of the (π1d3/2-1 ν(fp)2+) configuration with the (π2s1/2-1 ν(fp)0+) is needed to reproduce the measured magnetic moment of 49K. Furthermore, all even-A potassium isotopes have dominant configuration arising from a hole in π1d3/2 coupled to the neutron in ν(fp). However, only in 48K the wave-function is found to be very fragmented with considerable amount originating from (π2s1/2-1 ν(fp)). The experimental results were compared to shell-model calculations using two different interactions: SDPF-NR and SDPF-U. Based on the direct measurement of the isomer shift in 38K performed during the experiment, we were able to to extract the difference in mean-square charge radii between the ground (I = 3+) and isomeric (I = 0+) states. It was found that the mean-square charge radius of the isomeric state is by 0.100(6) fm2 larger than the ground state. Our result contradicts the conclusion based on an indirect measurement, claiming that these two states have similar nuclear charge radii. [1] J. Papuga et al., Physical Review Letters 110, 172503 (2013) [2] J. Papuga et al., Physical Review C 90, 04321 (2014) [3] M. L. Bissell, J. Papuga et al., Physical Review Letters 113,052502 (2014)status: publishe