Abstract
Interaction cross sections σ I for 58–77 Ni on a carbon target at 280 MeV / nucleon were measured at the RIKEN Radioactive Isotope Beam Factory (RIBF) using the BigRIPS fragment separator. The aim of this work is to deduce matter radii from the measured values of σ I through Glauber-model analysis and, by combining them with the charge radii that have been precisely determined by the laser spectroscopy, to determine the neutron-skin thickness r np of Ni isotopes over a wide range of neutron excess δ = ( N Z )/ A from 0.03 to 0.27. The present data of σ I constitute the first systematic set along the isotopic chain in the Ni mass region, providing a consistent basis for investigating the evolution of nuclear size and neutron-skin with increasing neutron excess. The slope of the neutron-skin thickness r np as a function of the neutron excess δ is expected to provide an important constraint on the L parameter of the nuclear matter equation of state (EOS), which represents the first-order term in the density dependence of the symmetry energy in nuclear matter. The EOS is essential for understanding not only the structure of atomic nuclei but also the mechanisms of supernova explosions and the properties of neutron stars. The results of this study are therefore expected to provide valuable insights into the elucidation of the EOS.