D. Voulot, S. J. Freeman, P. Van Duppen, Liam Gaffney, J. F. Smith, M. Zielinska, Herbert Hess, R. Orlandi, Mark Huyse, Kathrin Wimmer, M. Seidlitz, Michaël Bender, P. Peura, N. Bree, Marcus Scheck, Alick Deacon, D. Muecher, K. Geibel, D. G. Jenkins, A P Robinson, R. Wadsworth, H. De Witte, Janne Pakarinen, A. Blazhev, P. Reiter, V. Kumar, Paul-Henri Heenen, Jan Diriken, Andreas Ekström, Douglas D. DiJulio, K. Singh, Ch. Fransen, Baharak Hadinia, J. Van de Walle, O. Ivanov, Tuomas Grahn, Fredrik Wenander, Th. Kroell, P. A. Butler, S. Martin-Haugh, Panu Rahkila, K. Wrzosek-Lipska, Joonas Konki, B. Bruyneel, U. Jakobsson, N. Kesteloot, Thomas Davinson, N. Warr, A. Petts, Thomas Elias Cocolios, M. Hass, Andrei Andreyev, Department of Chemistry [Cambridge, UK], University of Cambridge [UK] (CAM), Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), Université Sciences et Technologies - Bordeaux 1-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Institut du Cerveau et de la Moëlle Epinière = Brain and Spine Institute (ICM), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-CHU Pitié-Salpêtrière [AP-HP], Sorbonne Université (SU)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP), CSIR-National Institute of Oceanography, Gravitational-Wave Physics and Astronomy Center (GWPAC), California State University [Fullerton] (CSU), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de la Santé et de la Recherche Médicale (INSERM)-CHU Pitié-Salpêtrière [AP-HP], and Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
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 α-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 Rn202 and Rn204 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 21+ state was extracted for both Rn202 and Rn204, corresponding to B(E2;21+→01+)=29-8+8 and 43-12+17 W.u. respectively. Additionally, E2 matrix elements connecting the 21+ state with the 41+ and 22+ states were determined in Rn202. 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., 0, SCOPUS: ar.j, info:eu-repo/semantics/published