CERN Accelerating science

Article
Report number	arXiv:2012.01864
Title	Charge radii of exotic potassium isotopes challenge nuclear theory and the magic character of $N = 32$
Author(s)	Koszorús, Á. (Leuven U.) ; Yang, X.F. (Peking U., SKLNPT) ; Jiang, W.G. (U. Tennessee, Knoxville ; Oak Ridge ; Chalmers U. Tech.) ; Novario, S.J. (U. Tennessee, Knoxville ; Oak Ridge) ; Bai, S.W. (Peking U., SKLNPT) ; Billowes, J. (Manchester U.) ; Binnersley, C.L. (Manchester U.) ; Bissell, M.L. (Manchester U.) ; Cocolios, T.E. (Leuven U.) ; Cooper, B.S. (Manchester U.) ; de Groote, R.P. (Jyvaskyla U. ; Helsinki U.) ; Ekström, A. (Chalmers U. Tech.) ; Flanagan, K.T. (Manchester U.) ; Forssén, C. (Chalmers U. Tech.) ; Franchoo, S. (Orsay, IPN) ; Ruiz, R.F. Garcia (CERN ; MIT, Cambridge, Dept. Phys.) ; Gustafsson, F.P. (Leuven U.) ; Hagen, G. (Oak Ridge ; U. Tennessee, Knoxville) ; Jansen, G.R. (Oak Ridge) ; Kanellakopoulos, A. (Leuven U.) ; Kortelainen, M. (Jyvaskyla U. ; Helsinki U.) ; Nazarewicz, W. (Michigan State U.) ; Neyens, G. (Leuven U. ; CERN) ; Papenbrock, T. (U. Tennessee, Knoxville ; Oak Ridge) ; Reinhard, P.-G. (U. Erlangen-Nuremberg (main)) ; Sahoo, B.K. (Ahmedabad U.) ; Ricketts, C.M. (Manchester U.) ; Vernon, A.R. (Leuven U. ; Manchester U.) ; Wilkins, S.G. (CERN)
Publication	2021-01-28
Imprint	2020-12-03
Number of pages	5
Note	submitted version; revision accepted in Nature Physics
In:	Nature Phys. 17, 4 (2021) pp.439-443 Nature Phys. 17 (2021) pp.539
DOI	10.1038/s41567-020-01136-5 (publication) 10.1038/s41567-021-01192-5 (erratum)
Subject category	physics.atom-ph ; Other Fields of Physics ; nucl-th ; Nuclear Physics - Theory ; nucl-ex ; Nuclear Physics - Experiment
Abstract	Nuclear charge radii are sensitive probes of different aspects of the nucleon-nucleon interaction and the bulk properties of nuclear matter; thus, they provide a stringent test and challenge for nuclear theory. The calcium region has been of particular interest, as experimental evidence has suggested a new magic number at $N = 32$ [1-3], while the unexpectedly large increases in the charge radii [4,5] open new questions about the evolution of nuclear size in neutron-rich systems. By combining the collinear resonance ionization spectroscopy method with $\beta$-decay detection, we were able to extend the charge radii measurement of potassium ($Z =19$) isotopes up to the exotic $^{52}$K ($t_{1/2}$ = 110 ms), produced in minute quantities. Our work provides the first charge radii measurement beyond $N = 32$ in the region, revealing no signature of the magic character at this neutron number. The results are interpreted with two state-of-the-art nuclear theories. For the first time, a long sequence of isotopes could be calculated with coupled-cluster calculations based on newly developed nuclear interactions. The strong increase in the charge radii beyond $N = 28$ is not well captured by these calculations, but is well reproduced by Fayans nuclear density functional theory, which, however, overestimates the odd-even staggering effect. These findings highlight our limited understanding on the nuclear size of neutron-rich systems, and expose pressing problems that are present in some of the best current models of nuclear theory.
Copyright/License	preprint: (License: arXiv nonexclusive-distrib 1.0) publication: © 2021-2025 The Author(s) (License: CC-BY-4.0)

Corresponding record in: Inspire