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First observation of a shape isomer and a low-lying strongly-coupled prolate band in neutron-deficient semi-magic 187Pb

Journal Article · · Physics Letters. B
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  1. Chinese Academy of Sciences (CAS), Lanzhou (China); University of Chinese Academy of Sciences, Beijing (China)
  2. University of York (United Kingdom); Japan Atomic Energy Agency (JAEA), Tokai (Japan)
  3. Argonne National Laboratory (ANL), Argonne, IL (United States)
  4. Peking University, Beijing (China)
  5. Chinese Academy of Sciences (CAS), Lanzhou (China); Peking University, Beijing (China)
  6. University of Surrey, Guildford (United Kingdom)
  7. NRC Kurchatov Institute, Gatchina (Russia)
  8. Katholieke University Leuven, Heverlee (Belgium)
  9. University of York (United Kingdom)
  10. Comenius University, Bratislava (Slovakia)
  11. Helmholtz-Institut Mainz, Mainz (Germany); GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt (Germany); Johannes Gutenberg University, Mainz (Germany)
  12. European Organization for Nuclear Research (CERN), Geneva (Switzerland)
  13. Helmholtz-Institut Mainz, Mainz (Germany); GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt (Germany)
  14. Chinese Academy of Sciences (CAS), Lanzhou (China); University of Chinese Academy of Sciences, Beijing (China); Argonne National Laboratory (ANL), Argonne, IL (United States)
  15. GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt (Germany)
  16. Lanzhou University (China)
  17. Louisiana State University, Baton Rouge, LA (United States)
+ Show Author Affiliations
Prompt and delayed gamma-ray spectroscopy of the neutron-deficient, semi-magic isotope 187Pb has been performed using the recoil-decay and isomer-decay tagging techniques at the Argonne Gas-Filled Analyzer. A new 5.15(15)-mu s isomeric state at only 308 keV above the spherical 3/2- ground state is identified and classified as a shape isomer. A strongly-coupled band is observed on top of the isomer, which is nearly identical to the one built on the prolate 7/2-[514] Nilsson state in the isotone 185Hg. Based on this similarity and on the result of the potential-energy surface calculations, the new isomer in 187Pb is proposed to originate from the same configuration. The retarded character of the 308-keV (7/2(-)→ 3/2$$_{gs}^{-}$$ transition with a deduced B(E2) = 5.6(2) x 10-4 W.u. can be well explained by the significant difference between the prolate parent and spherical daughter configurations, leading to the shape isomerism. The excitation energy of the isomer is surprisingly low, being roughly half of the excitation energies of the known 0+ intruder bandheads in the neighboring 186,188Pb isotopes. The combined results of the present work and the previous alpha-decay and laser spectroscopy studies present evidence for triple shape coexistence at low energy in the negative-parity configurations of 187Pb, which is well reproduced by the potential-energy surface calculations.
Research Organization:
Argonne National Laboratory (ANL), Argonne, IL (United States)
Sponsoring Organization:
Chinese Academy of Sciences; National Key R&D Program of China; National Natural Science Foundation of China; Science and Technology Facilities Council (STFC); USDOE Office of Science (SC), Nuclear Physics (NP)
Grant/Contract Number:
AC02-06CH11357; FG02-97ER41033
OSTI ID:
1902640
Journal Information:
Physics Letters. B, Journal Name: Physics Letters. B Vol. 829; ISSN 0370-2693
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English

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Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
PES calculations
isomeric state
rotational band
shape coexistence