Reassigning the shapes of the 0+ states in the 186Pb nucleus

Joonas Ojala, Janne Pakarinen*, Philippos Papadakis, Juha Sorri, Mikael Sandzelius, Daniel M. Cox, Kalle Auranen, Hussam Badran, Paul J. Davies, Tuomas Grahn, Paul T. Greenlees, Jack Henderson, Andrej Herzáň, Rolf Dietmar Herzberg, Joshua Hilton, Ulrika Jakobsson, David G. Jenkins, David T. Joss, Rauno Julin, Sakari JuutinenTibor Kibédi, Joonas Konki, Gregory J. Lane, Matti Leino, Jarkko Liimatainen, Christopher G. McPeake, Olavi Neuvonen, Robert D. Page, Edward Parr, Jari Partanen, Pauli Peura, Panu Rahkila, John Revill, Panu Ruotsalainen, Jan Sarén, Catherine Scholey, Sanna Stolze, Juha Uusitalo, Andrew Ward, Robert Wadsworth

*Corresponding author for this work

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Across the physics disciplines, the 186Pb 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 186Pb were determined in a simultaneous in-beam γ-ray and electron spectroscopy experiment employing the recoil-decay tagging technique. The feeding of the 02+ state and the interband 22+→21+ 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;21+→02+) value of 190(80) W.u., the transitional quadrupole moment ∣Qt(21+→02+)∣=7.7(33) eb and intensity balance arguments provide evidence to reassign the 02+ and 03+ 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.

Original languageEnglish
Article number213
JournalCommunications Physics
Issue number1
Publication statusPublished - 18 Aug 2022

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