Collectivity in the light radon nuclei measured directly via Coulomb excitation

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, D. DiJulio, J. Diriken, A. Ekstrom, Ch. Fransen, S. J. Freeman, K. Geibel, T. GrahnB. 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

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

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.

Original languageEnglish
Article number064313
Number of pages11
JournalPhysical Review C
Volume91
Issue number6
DOIs
Publication statusPublished - 22 Jun 2015

Keywords

  • CORRELATED RADIOACTIVE DECAY
  • SHAPE COEXISTENCE
  • MERCURY ISOTOPES
  • DROPLET-MODEL
  • GAMMA-DECAY
  • DATA SHEETS
  • STATES
  • AG-109
  • ISOLDE
  • TRANSITION

Cite this