Shell structure: ~ 1 MeV Quantum phase transitions: ~ 100s keV Collective effects: ~ 100s keV Interaction filters: ~ 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

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

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

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

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 Largest p-n interactions if proton and neutron shells have filling fractional filling

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 keV level. But quantitative microscopic calculations needed

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

Backups

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

 Z  82, N < Z > 82, N < Z > 82, N > 126

208 Hg

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

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