Electromagnetic Moments of Radioactive Te 136 and the Emergence of Collectivity 2 p a2 n Outside of Double-Magic Sn 132

Radioactive Te136 has two valence protons and two valence neutrons outside of the Sn132 double shell closure, providing a simple laboratory for exploring the emergence of collectivity and nucleon-nucleon interactions. Coulomb excitation of Te136 on a titanium target was utilized to determine an extensive set of electromagnetic moments for the three lowest-lying states, including B(E2;01+→21+), Q(21+), and g(21+). The results indicate that the first-excited state, 21+, composed of the simple 2pa2n system, is prolate deformed, and its wave function is dominated by excited valence neutron configurations, but not to the extent previously suggested. It is demonstrated that extreme sensitivity of g(21+) to the proton and neutron contributions to the wave function provides unique insight into the nature of emerging collectivity, and g(21+) was used to differentiate among several state-of-the-art theoretical calculations. Our results are best described by the most recent shell model calculations.