The Ca region (Z=20) has attracted significant experimental and theoretical attention due to the proposed shell closures at neutron numbers N=32,34 [1-3]. The subshell closure at N=32 in particular represents a puzzling case, since the unexpectedly large charge radius of 52Ca  challenges the magicity of this isotope. With one proton hole in the Z=20 shell and 33 neutrons, 52K is a key isotope for pinning down the nuclear forces around N=32.
The hyperfine structure of 52K was measured with the Collinear Resonance Ionization Spectroscopy (CRIS) technique . This work demonstrates for the first time the combination of the CRIS method with beta-detection, paving the way for future measurements on beams that are heavily contaminated with stable or long lived isotopes.
In this contribution, the ground state properties of 52K will be discussed, showing that the combined information of nuclear spin, magnetic moment and changes in the mean-square charge radii contributes to understanding the structure of this isotope and the N=32 region.
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