Collectivity in the light radon nuclei measured directly via Coulomb excitation

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Background: Shape coexistence in heavy nuclei poses a strong challenge to state-of-the-art nuclear models, where several competing shape minima are found close to the ground state. A classic region for investigating this phenomenon is in the region around Z = 82 and the neutron midshell at N = 104. Purpose: Evidence for shape coexistence has been inferred from a-decay measurements, laser spectroscopy, and in-beam measurements. While the latter allow the pattern of excited states and rotational band structures to be mapped out, a detailed understanding of shape coexistence can only come from measurements of electromagnetic matrix elements. Method: Secondary, radioactive ion beams of Rn-202 and Rn-204 were studied by means of low-energy Coulomb excitation at the REX-ISOLDE in CERN. Results: The electric-quadrupole (E2) matrix element connecting the ground state and first excited 2(1)(+) state was extracted for both Rn-202 and Rn-204, corresponding to B(E2; 2(1)(+) -> 0(1)(+)) = 29(-8)(+8) and 43(-12)(+17) W.u., respectively. Additionally, E2 matrix elements connecting the 2(1)(+) state with the 4(1)(+) and 2(2)(+) states were determined in Rn-202. No excited 0(+) states were observed in the current data set, possibly owing to a limited population of second-order processes at the currently available beam energies. Conclusions: The results are discussed in terms of collectivity and the deformation of both nuclei studied is deduced to be weak, as expected from the low-lying level-energy schemes. Comparisons are also made to state-of-the-art beyond-mean-field model calculations and the magnitude of the transitional quadrupole moments are well reproduced.


  • L. P. Gaffney
  • A. P. Robinson
  • D. G. Jenkins
  • A. N. Andreyev
  • M. Bender
  • A. Blazhev
  • N. Bree
  • B. Bruyneel
  • P. A. Butler
  • T. E. Cocolios
  • T. Davinson
  • A. N. Deacon
  • H. De Witte
  • Douglas DiJulio
  • J. Diriken
  • Andreas Ekström
  • Ch. Fransen
  • S. J. Freeman
  • K. Geibel
  • T. Grahn
  • And 32 others
  • B. Hadinia
  • M. Hass
  • P. -H. Heenen
  • H. Hess
  • M. Huyse
  • U. Jakobsson
  • N. Kesteloot
  • J. Konki
  • Th. Kroell
  • V. Kumar
  • O. Ivanov
  • S. Martin-Haugh
  • D. Muecher
  • R. Orlandi
  • J. Pakarinen
  • A. Petts
  • P. Peura
  • P. Rahkila
  • P. Reiter
  • M. Scheck
  • M. Seidlitz
  • K. Singh
  • J. F. Smith
  • J. Van de Walle
  • P. Van Duppen
  • D. Voulot
  • R. Wadsworth
  • N. Warr
  • F. Wenander
  • K. Wimmer
  • K. Wrzosek-Lipska
  • M. Zielinska
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Subatomic Physics
Original languageEnglish
Article number064313
JournalPhysical Review C (Nuclear Physics)
Issue number6
Publication statusPublished - 2015
Publication categoryResearch