Reassigning the shapes of the 0<SUP>+</SUP> states in the <SUP>186</SUP>Pb nucleus



Ojala, Joonas ORCID: 0000-0002-3889-5837, Pakarinen, Janne, Papadakis, Philippos ORCID: 0000-0001-7509-4257, Sorri, Juha, Sandzelius, Mikael, Cox, Daniel M, Auranen, Kalle, Badran, Hussam, Davies, Paul J, Grahn, Tuomas
et al (show 30 more authors) (2022) Reassigning the shapes of the 0<SUP>+</SUP> states in the <SUP>186</SUP>Pb nucleus. COMMUNICATIONS PHYSICS, 5 (1).

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Abstract

<jats:title>Abstract</jats:title><jats:p>Across the physics disciplines, the <jats:sup>186</jats:sup>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 <jats:sup>186</jats:sup>Pb were determined in a simultaneous in-beam <jats:italic>γ</jats:italic>-ray and electron spectroscopy experiment employing the recoil-decay tagging technique. The feeding of the <jats:inline-formula><jats:alternatives><jats:tex-math>$${0}_{2}^{+}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> </mml:mrow> </mml:msubsup> </mml:math></jats:alternatives></jats:inline-formula> state and the interband <jats:inline-formula><jats:alternatives><jats:tex-math>$${2}_{2}^{+}\to {2}_{1}^{+}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> </mml:mrow> </mml:msubsup> <mml:mo>→</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>1</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> </mml:mrow> </mml:msubsup> </mml:math></jats:alternatives></jats:inline-formula> transition have been observed. We also present direct measurement of the energies of the electric monopole transitions from the excited 0<jats:sup>+</jats:sup> states to the 0<jats:sup>+</jats:sup> ground state. In contrast to the earlier understanding, the obtained reduced transition probability <jats:inline-formula><jats:alternatives><jats:tex-math>$$B(E2;{2}_{1}^{+}\to {0}_{2}^{+})$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>B</mml:mi> <mml:mrow> <mml:mo>(</mml:mo> <mml:mrow> <mml:mi>E</mml:mi> <mml:mn>2</mml:mn> <mml:mo>;</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>1</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> </mml:mrow> </mml:msubsup> <mml:mo>→</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> </mml:mrow> </mml:msubsup> </mml:mrow> <mml:mo>)</mml:mo> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> value of 190(80) W.u., the transitional quadrupole moment <jats:inline-formula><jats:alternatives><jats:tex-math>$$| {Q}_{t}({2}_{1}^{+}\to {0}_{2}^{+})| =7.7$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mo>∣</mml:mo> <mml:msub> <mml:mrow> <mml:mi>Q</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>t</mml:mi> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo>(</mml:mo> <mml:mrow> <mml:msubsup> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>1</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> </mml:mrow> </mml:msubsup> <mml:mo>→</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> </mml:mrow> </mml:msubsup> </mml:mrow> <mml:mo>)</mml:mo> </mml:mrow> <mml:mo>∣</mml:mo> <mml:mo>=</mml:mo> <mml:mn>7.7</mml:mn> </mml:math></jats:alternatives></jats:inline-formula>(33) eb and intensity balance arguments provide evidence to reassign the <jats:inline-formula><jats:alternatives><jats:tex-math>$${0}_{2}^{+}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> </mml:mrow> </mml:msubsup> </mml:math></jats:alternatives></jats:inline-formula> and <jats:inline-formula><jats:alternatives><jats:tex-math>$${0}_{3}^{+}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> </mml:mrow> </mml:msubsup> </mml:math></jats:alternatives></jats:inline-formula> 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.</jats:p>

Item Type: Article
Divisions: Faculty of Science and Engineering > School of Physical Sciences
Depositing User: Symplectic Admin
Date Deposited: 30 Aug 2022 11:58
Last Modified: 08 Oct 2023 15:17
DOI: 10.1038/s42005-022-00990-4
Open Access URL: https://doi.org/10.1038/s42005-022-00990-4
Related URLs:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3162812