Two-neutron and core-excited states in Pb210: Tracing E3 collectivity and evidence for a new β-decaying isomer in Tl210

R. Broda, Ł. W. Iskra, R. V. F. Janssens, B. A. Brown, B. Fornal, J. Wrzesiński, N. Cieplicka-Oryńczak, M. P. Carpenter, C. J. Chiara, C. R. Hoffman, F. G. Kondev, G. J. Lane, T. Lauritsen, Zs. Podolyák, D. Seweryniak, W. B. Walters, and S. Zhu
Phys. Rev. C 98, 024324 – Published 31 August 2018

Abstract

Yrast and near-yrast levels up to an I=17 spin value and a 6-MeV excitation energy have been delineated in the “two-neutron” Pb210 nucleus following deep-inelastic reactions involving Pb208 targets and a number of heavy-ion beams at energies 25% above the Coulomb barrier. The level scheme was established on the basis of multifold prompt and delayed coincidence relationships measured with the Gammasphere array. In addition to the previously known states, many new levels were identified. For most of the strongly populated states, spin-parity assignments are proposed on the basis of angular distributions. The reinvestigation of the ν(g9/2)2, 8+ isomeric decay results in the firm identification of the low-energy E2 transitions involved in the 8+6+4+ cascade, and in a revised 6+ level half-life of 92(10) ns, nearly a factor of 2 longer than previously measured. Among the newly identified states figure spin I=410 levels associated with the νg9/2i11/2 multiplet, as well as yrast states involving νg9/2j15/2, νi11/2j15/2, and ν(j15/2)2 neutron couplings. The highest-spin excitations are understood as 1p1h core excitations and the yrast population is found to be fragmented to the extent that levels of spin higher than I=17 could not be reached. Four E3 transitions are present in the Pb210 yrast decay; three of these involve the g9/2j15/2 octupole component, as reflected in the 21(2) and >10 Weisskopf unit enhancements of the B(E3) rates of the first two. The fourth, 16+13E3 transition corresponds to the 3 core octupole excitation built on the νi11/2j15/2 state, in analogy to a similar E3 coupling to the νj15/2 level in Pb209. Shell-model calculations performed for two-neutron states and 1p1h Pb208 core excitations are in good agreement with the data. Evidence was found for the existence of a hitherto unknown high-spin β-decaying isomer in Tl210. Shell-model calculations of the Tl210 levels suggest the possibility of a 11+ long-lived, β-decaying state, and the delayed yields observed in various reactions fit rather well with a Tl210 assignment.

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  • Received 11 May 2018

DOI:https://doi.org/10.1103/PhysRevC.98.024324

©2018 American Physical Society

Physics Subject Headings (PhySH)

Nuclear Physics

Authors & Affiliations

R. Broda1, Ł. W. Iskra1, R. V. F. Janssens2, B. A. Brown3, B. Fornal1, J. Wrzesiński1, N. Cieplicka-Oryńczak1, M. P. Carpenter4, C. J. Chiara4,5,*, C. R. Hoffman4, F. G. Kondev4, G. J. Lane6, T. Lauritsen4, Zs. Podolyák7, D. Seweryniak4, W. B. Walters5, and S. Zhu4

  • 1Institute of Nuclear Physics, Polish Academy of Sciences, PL-31-342 Kraków, Poland
  • 2Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA and Triangle Universities Nuclear Laboratory, Duke University, Durham, North Carolina 27708, USA
  • 3Department of Physics and Astronomy and National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824-1321, USA
  • 4Physics Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
  • 5Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA
  • 6Department of Nuclear Physics, Research School of Physics & Engineering, Australian National University, Canberra, A. C. T. 2601, Australia
  • 7Department of Physics, University of Surrey, Guildford GU2 7XH, United Kingdom

  • *Present address: US Army Research Laboratory, Adelphi, Maryland 20783, USA.

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Issue

Vol. 98, Iss. 2 — August 2018

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