Isospin and Z1/3-dependence of the nuclear charge radii

Abstract

Based on the systematic investigation of the data available for nuclei with A≥ 40, a Z 1/3-dependence for the nuclear charge radii is shown to be superior to the generally accepted A 1/3 law. A delicate scattering of data around R c/Z 1/3 is inferred as owing to the isospin effect and a linear dependence of R c/Z 1/3 on N/Z (or (N - Z)/2) is found. This inference is well supported by the microscopic Relativistic Continuum Hartree-Bogoliubov (RCHB) calculation conducted for the proton magic Ca, Ni, Zr, Sn and Pb isotopes including the exotic nuclei close to the neutron drip line. With the linear isospin dependence provided by the data and RCHB theory, a new isospin-dependent Z 1/3 formula for the nuclear charge radii is proposed.