I'm doing some self-study and I'm attempting to calculate the energies needed to overcome the Coulomb barrier. I stumbled upon $R = r_0A^{1/3}$ for the radius of nuclei. I've been looking around online and I've seen that r0 is equal to 1.3E-15.
But I can't find out why it's equal to that, and where it comes from, any help would be fantastic!