Mass Measurements of Exotic Ar 48 − 50 Isotopes: Probing Proton-Neutron Interaction of the Doubly Magic Ca 52 and the Robustness of N = 32 Subshell

This is the authors' abstract. We don't add key points for this paper.

High-precision multireflection time-of-flight mass spectrometry has been applied at BigRIPS-SLOWRI of the Radioactive Isotope Beam Factory (RIBF). The atomic mass of ⁵⁰Ar was measured for the first time, and the mass value of ⁴⁹Ar was determined to be 674 keV lower than the one from a previous Bρ- TOF measurement, with a precision improved by a factor of 250. The new mass data enable us to determine the empirical proton-neutron interaction strength in the unconventional doubly magic nucleus ⁵²Ca. This strength exhibits a conspicuous variation across shell closures, analogously to what observed in classical doubly magic nuclei. Meanwhile, our measurements support the existence of a weak shell effect at N=32 in Ar isotopes. To supplement these experimental findings, theoretical calculations were performed for the isotopes of interest, which, compared with data, illustrate the capacity of ab initio expansion methods to capture key quadrupole correlations in doubly open-shell nuclei via an explicit account of nuclear deformation.