Structure of the doubly midshell nucleus ₆₆¹⁷⁰Dy₁₀₄

Potentional energy surface calculations for the doubly midshell nucleus ₆₆¹⁷⁰Dy₁₀₄ support a variety of extreme properties. The ground-state deformation is among the largest in the region, consistent with it having the maximal value of valence particles for any nucleus below the ²⁰⁸Pb doubly closed shell. The energy minimum is found to be remarkably constant in the (β₂,γ) plane as a function of angular momentum. The nucleus is predicted to undergo a dual alignment with midshell high-j protons and neutrons aligning simultaneously at spin ≈14ħ. Configuration-constrained calculations for the two-quasiparticle configurations predict the presence of a low-lying K^π=6⁺ state with a similar axially symmetric shape to the highly deformed ground state.