Effect of valence nucleons on RMS charge radii and surface thickness

Abstract

The nucleonic promiscuity factor P=NpNn/(Np+Nn), where Np(Nn) is the number of valence protons (neutrons) or holes, is shown to be a useful and physically meaningful parameter in the description of RMS charge radii. The introduction of P in the radius formula R approximately=Rc+0.07P/Rc (Rc; droplet model 'closed-shell radius') reduces the chi 2/n' value by a factor of three. The empirically found mass number dependence of the P-dependent contribution to radii is in agreement with the qualitative theoretical expectation for the average strength of the isoscalar p-n interaction. A significant correlation between surface diffusity and promiscuity as well as between diffusity and radius is pointed out.