Cause of the charge radius isotope shift at the \emph{N}=126 shell gap

We discuss the mechanism causing the `kink' in the charge radius isotope shift at the N=126 shell closure. The occupation of the 1$i_{11/2}$ neutron orbital is the decisive factor for reproducing the experimentally observed kink. We investigate whether this orbital is occupied or not by different Skyrme effective interactions as neutrons are added above the shell closure. Our results demonstrate that several factors can cause an appreciable occupation of the 1$i_{11/2}$ neutron orbital, including the magnitude of the spin-orbit field, and the isoscalar effective mass of the Skyrme interaction. The symmetry energy of the effective interaction has little influence upon its ability to reproduce the kink.Comment: 4 pages, 4 figures, to be submitted to proceedings of INPC 201

Shapes and Dynamics from the Time-Dependent Mean Field

Explaining observed properties in terms of underlying shape degrees of freedom is a well--established prism with which to understand atomic nuclei. Self--consistent mean--field models provide one tool to understand nuclear shapes, and their link to other nuclear properties and observables. We present examples of how the time--dependent extension of the mean--field approach can be used in particular to shed light on nuclear shape properties, particularly looking at the giant resonances built on deformed nuclear ground states, and at dynamics in highly-deformed fission isomers. Example calculations are shown of $^{28}$Si in the first case, and $^{240}$Pu in the latter case.Comment: 9 pages, 5 figures, to appear in proceedings of International Workshop "Shapes and Dynamics of Atomic Nuclei: Contemporary Aspects" (SDANCA-15), 8-10 October 2015, Sofia, Bulgari

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.Comment: 5 pages, 5 figure