Publication
Reassigning the shapes of the 0+ states in the 186Pb nucleus
Publisher:
Springer Science and Business Media LLC
Date:
18-08-2022
DOI:
10.1038/S42005-022-00990-4
Abstract: Across the physics disciplines, the 186 Pb nucleus is the only known system, where the two first excited states, together with the ground state, form a triplet of zero-spin states assigned with prolate, oblate and spherical shapes. Here we report on a precision measurement where the properties of collective transitions in 186 Pb were determined in a simultaneous in-beam γ -ray and electron spectroscopy experiment employing the recoil-decay tagging technique. The feeding of the $${0}_{2}^{+}$$ 0 2 + state and the interband $${2}_{2}^{+}\to {2}_{1}^{+}$$ 2 2 + → 2 1 + transition have been observed. We also present direct measurement of the energies of the electric monopole transitions from the excited 0 + states to the 0 + ground state. In contrast to the earlier understanding, the obtained reduced transition probability $$B(E2 {2}_{1}^{+}\to {0}_{2}^{+})$$ B ( E 2 2 1 + → 0 2 + ) value of 190(80) W.u., the transitional quadrupole moment $$| {Q}_{t}({2}_{1}^{+}\to {0}_{2}^{+})| =7.7$$ ∣ Q t ( 2 1 + → 0 2 + ) ∣ = 7.7 (33) eb and intensity balance arguments provide evidence to reassign the $${0}_{2}^{+}$$ 0 2 + and $${0}_{3}^{+}$$ 0 3 + states with predominantly prolate and oblate shape, respectively. Our work demonstrates a step-up in experimental sensitivity and paves the way for systematic studies of electric monopole transitions in this region. These electric monopole transitions probe the nuclear volume in a unique manner and provide unexploited input for development of the next-generation energy density functional models.