Why is lead so kinky?
  We revisit the problem of the kink in the charge radius shift of neutron-rich even lead isotopes. We show that the ability of a Skyrme force to reproduce the isotope shift is determined by the occupation of the neutron 1i11/2 orbital beyond N=126 and the corresponding change it causes to deeply-bound protons orbitals with a principal quantum number of 1. Given the observed position of the single-particle energies, one must either ensure occupation is allowed through correlations, or not demand that the single-particle energies agree with experimental values at the mean-field level. 
P. M. Goddard (1), P. D. Stevenson (1) and A. Rios (1) ((1) University   of Surrey)
nucl-th nucl-ex