In this paper we study the neutron-number dependence of $\delta R$ (difference of nuclear charge radii $R$ for two nuclei of one isotope chain), based on which we suggest an empirical formula of $\delta R$, called the $\delta R$ relations. The $\delta R$ relations of a number of theoretical models are also investigated in this work. We demonstrate that the $\delta R$ relations of this work are more competitive than the previously called $\delta R_{in-jp}$ relations, with the virtue of simplicity and flexibility. By using this approach we tabulate our predicted results of 1647 nuclear charge radii which are experimentally unaccessible, within theoretical uncertainty below 0.03 fm.

• Received 22 October 2020
• Revised 23 April 2021
• Accepted 1 June 2021

DOI:https://doi.org/10.1103/PhysRevC.104.014303