Effective Charge of Neutrons in Nuclei

The polarization of closed proton shells by neutrons can be considered as inducing an effective charge on the neutron for some multipoles but not for others. The rough constancy of the effective neutron charge as observed in $E2\mathrm{}$ transitions and quadrupole moments in nondeformed odd $N$-even $Z$ nuclei is discussed, and arguments are presented to explain this phenomenon along the lines of the shell model.