Electromagnetic Moments of Radioactive ¹³⁶Te and the Emergence of Collectivity 2p ⊕ 2n outside of Double-Magic ¹³²Sn

Radioactive ¹³⁶Te has two valence protons and two valence neutrons outside of the ¹³²Sn double shell closure, providing a simple laboratory for exploring the emergence of collectivity and nucleon- nucleon interactions. Coulomb excitation of ¹³⁶Te on a titanium target was utilized to determine an extensive set of electromagnetic moments for the three lowest-lying states, including B(E2;0(+/1)→ 2(+/1)), Q(2(+/1)), and g(2(+/1)). The results indicate that the first-excited state, 2(+/1) , composed of the simple 2p ⊕ 2n system, is prolate deformed, and its wave function is dominated by neutron degrees of freedom, but not to the extent previously suggested. It is demonstrated that extreme sensitivity of g(2(+/1)) to the proton and neutron contributions to the wave function provides unique insight into the nature of emerging collectivity, and g(2(+/1)) was used to differentiate among several state-of-the-art theoretical calculations. Finally, our results are best described by the most recent shell model calculations.