The strength of the N = 28 magic number in neutron-rich argon isotopes is examined through high-precision mass measurements of 46−48Ar, performed with the ISOLTRAP mass spectrometer at ISOLDE/CERN. The new mass values are up to 90 times more precise than previous measurements. While they suggest the persistence of the N = 28 shell closure for argon, we show that this conclusion has to be nuanced in light of the wealth of spectroscopic data and theoretical investigations performed with the \emph{SDPF-U} phenomenological shell model interaction. Our results are also compared with \emph{ab initio} calculations using the Valence Space In-Medium Similarity Renormalization Group and the Self-Consistent Green's Function approaches. Both calculations provide a very good account of mass systematics at and around Z = 18 and, generally, a consistent description of the physics in this region. This combined analysis indicates that 46Ar is the transition between the closed-shell 48Ca and collective 44S.
@article{arxiv.2006.02712,
title = {Examining the $N$ = 28 shell closure through high-precision mass measurements of $^{46-48}$Ar},
author = {Maxime Mougeot and Dinko Atanasov and Carlo Barbieri and Klaus Blaum and Martin Breitenfeld and Antoine de Roubin and Thomas Duguet and Sebastian George and Frank Herfurth and Alexander Herlert and Jason D. Holt and Jonas Karthein and David Lunney and Vladimir Manea and Petr Navràtil and Dennis Neidherr and Marco Rosenbusch and Lutz Schweikhard and Achim Schwenk and Vittorio Somà and Andree Welker and Frank Wienholtz and Robert N. Wolf and Kai Zuber},
journal= {arXiv preprint arXiv:2006.02712},
year = {2020}
}