« The charge radius of the 54Ni nucleus was determined using collinear laser spectroscopy at the BEam COoler and LAser spectroscopy (BECOLA) facility [1,2] at the National Superconducting Cyclotron Laboratory at Michigan State University. The 54Ni charge radius, together with the already known charge radius of its mirror partner 54Fe [3], has been used to determine the slope parameter L of the symmetry energy in the nuclear equation of state [4]. The linear correlation between the difference of charge radii ΔR_mirr and L [5] is used to set this constraint on L. Knowledge on L is critical for the extrapolation of the symmetry energy to higher density for predictions of properties of super-heavy nuclei and for understanding neutron stars [6] where the softness or stiffness of the equation of state has a direct link to the neutron star radius. Analyses on the 36Ca-36Ar pair [7] and 32Si-32Ar [8] determined at BECOLA and the GW170817 neutron star merger [9] suggest a relatively soft neutron equation of state compared to that obtained with the new PREX results. Results of the 54Ni-54Fe mirror pair and future perspectives will be discussed. »

References
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[6] A. W. Steiner et al., APJL 765, L5 (2013).
[7] B.A. Brown et al., PRR 2, 022035(R) (2020).
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[9] C.A. Raithel and F. Özel, Astrophys. J. 885, 121 (2019).