1. Shell structure: ~ 1 MeV Quantum phase transitions: ~ 100s keV Collective effects: ~ 100s keV Interaction filters: ~ 10-15 keV Binding energies, Separation energies: Collectivity, symmetries, quantum phase transitions What is the origin of simple patterns in complex nuclei? What is the origin of simple patterns in complex nuclei? Double differences of masses – Interaction filters: p-n interactions What is the nature of the nuclear force that binds protons and neutrons? Macro Micro Mass measurements of n-rich nuclei Collective Structure and the Microscopic Drivers of Structural Evolution

3. Collective contributions to masses can vary significantly for small parameter changes in collective models. Masses: complementary observable to spectroscopic data in pinning down structure. Particularly important far off stability where data will be sparse B.E (MeV) Examples of IBA calculations of rare earth nuclei B.E  S 2n (Coll.) for two calcs. S 2n (Coll.) for two calcs. ErGd

4. Valence Proton-Neutron Interaction Development of configuration mixing, collectivity and deformation – competition with pairing Changes in single particle energies and magic numbers Partial history: Goldhaber and de Shalit (1953); Talmi (1962); Federman and Pittel ( late 1970 ’ s); Casten et al (1981); Heyde et al (1980 ’ s); Nazarewicz, Dobacewski et al (1980 ’ s); Otsuka et al( 2000 ’ s) and many others. Microscopic perspective

5. Measurements of p-n Interaction Strengths Average p-n interaction between last two protons and last two neutrons  V pn (Z,N) = ¼ [ {B(Z,N) - B(Z, N-2)} - {B(Z-2, N) - B(Z-2, N-2)} ] Ref: J.-y. Zhang and J. D. Garrett

6. Orbit dependence of p-n interactions p-n interaction is short range similar orbits give larger p-n interactions HIGH j, LOW n LOW j, HIGH n 50 82 126 Largest p-n interactions if proton and neutron shells have filling fractional filling

7. Empirical p-n interaction strengths indeed strongest along diagonal. Empirical p-n interaction strengths stronger in like regions than unlike regions. New Xe masses (ISOLTRAP/ ISOLDE) Neidherr et al Nazarewicz, Stoitsov, Satula Though DFT gives masses only to ~ 1 MeV, the filter allows us to study subtle, important correlation effects at the 10-30 keV level. But quantitative microscopic calculations needed

8. Two regions of parabolic anomalies. Two regions of octupole correlations Possible signature?

9. Backups

10. Sn – Magic: no valence p-n interactions Both valence protons and neutrons N p N n Scheme Critical role of the valence p-n interaction

11.  82 50 82 126 Z  82, N < 126 1 1 1 2 Z > 82, N < 126 2 3 3 Z > 82, N > 126

12. 208 Hg

15. Direct correlation of observed growth rates of collectivity with empirical p-n interaction strengths p-n interactions and the evolution of structure

16. W. Nazarewicz, M. Stoitsov, W. Satula Microscopic Density Functional Calculations with Skyrme forces and different treatments of pairing Realistic Calculations