Charge radii of exotic potassium isotopes challenge nuclear theory and the magic character of $N = 32$
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| Format: | Preprint |
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2020
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| author | Koszorús, Á. Yang, X. F. Jiang, W. G. Novario, S. J. Bai, S. W. Billowes, J. Binnersley, C. L. Bissell, M. L. Cocolios, T. E. Cooper, B. S. de Groote, R. P. Ekström, A. Flanagan, K. T. Forssén, C. Franchoo, S. Ruiz, R. F. Garcia Gustafsson, F. P. Hagen, G. Jansen, G. R. Kanellakopoulos, A. Kortelainen, M. Nazarewicz, W. Neyens, G. Papenbrock, T. Reinhard, P. -G. Sahoo, B. K. Ricketts, C. M. Vernon, A. R. Wilkins, S. G. |
| author_facet | Koszorús, Á. Yang, X. F. Jiang, W. G. Novario, S. J. Bai, S. W. Billowes, J. Binnersley, C. L. Bissell, M. L. Cocolios, T. E. Cooper, B. S. de Groote, R. P. Ekström, A. Flanagan, K. T. Forssén, C. Franchoo, S. Ruiz, R. F. Garcia Gustafsson, F. P. Hagen, G. Jansen, G. R. Kanellakopoulos, A. Kortelainen, M. Nazarewicz, W. Neyens, G. Papenbrock, T. Reinhard, P. -G. Sahoo, B. K. Ricketts, C. M. Vernon, A. R. Wilkins, S. G. |
| contents | 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 $β$-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. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2012_01864 |
| institution | arXiv |
| publishDate | 2020 |
| record_format | arxiv |
| spellingShingle | Charge radii of exotic potassium isotopes challenge nuclear theory and the magic character of $N = 32$ Koszorús, Á. Yang, X. F. Jiang, W. G. Novario, S. J. Bai, S. W. Billowes, J. Binnersley, C. L. Bissell, M. L. Cocolios, T. E. Cooper, B. S. de Groote, R. P. Ekström, A. Flanagan, K. T. Forssén, C. Franchoo, S. Ruiz, R. F. Garcia Gustafsson, F. P. Hagen, G. Jansen, G. R. Kanellakopoulos, A. Kortelainen, M. Nazarewicz, W. Neyens, G. Papenbrock, T. Reinhard, P. -G. Sahoo, B. K. Ricketts, C. M. Vernon, A. R. Wilkins, S. G. Nuclear Experiment Nuclear Theory Atomic Physics 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 $β$-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. |
| title | Charge radii of exotic potassium isotopes challenge nuclear theory and the magic character of $N = 32$ |
| topic | Nuclear Experiment Nuclear Theory Atomic Physics |
| url | https://arxiv.org/abs/2012.01864 |