Do nuclei go pear-shaped? Coulomb excitation of ²²⁰Rn and ²²⁴Ra at REX-ISOLDE (CERN)

¹ School of Engineering, University of the West of Scotland, Paisley, PA1 2BE, UK
² SUPA, Scottish Universities Physics Alliance, Glasgow G12 8QQ, UK
³ Oliver Lodge Laboratory, Liverpool University, Liverpool L69 7ZE, UK
⁴ Instituut voor Kern- en Stralingsfysica KU Leuven, Leuven B-3001, Belgium
⁵ Dept. of Physics & Astronomy, University of Rochester, Rochester, NY 14627-0171, USA
⁶ ISOLDE, CERN, Geneva CH-1211, Switzerland
⁷ Institut für Kernphysik, Universität zu Köln, Köln D-50937, Germany
⁸ GANIL, Caen, BP 55027, F-14076, France
⁹ Institut für Kernphysik, Technische Universität Darmstadt, Darmstadt D-64289, Germany
¹⁰ Department of Nuclear Physics, Lund University, Lund PO Box 118, 221 00, Sweden
¹¹ Department of Physics, University of Michigan, Ann Arbor, Michigan 48104, USA
¹² School of Physics & Astronomy, University of Edinburgh, Edinburgh, EH9 3JZ, UK
¹³ Department of Physics, University of Jyväskylä, Jyväskylä FI-40014, Finland
¹⁴ Helsinki Institute of Physics, PO Box 64, FI-00014 Helsinki Finland
¹⁵ Department of Physics, University of York, York YO10 5DD, UK
¹⁶ Heavy Ion Laboratory, University of Warsaw, Warsaw 02-093, Poland
¹⁷ Physics Division, Lawrence Livermore National Laboratory, Livermore, California 94551, USA
¹⁸ Maier-Leibnitz-Laboratorium, Ludwig-Maximilians-Universität, Garching D-85748, Germany
¹⁹ Physik Department E12, Technische Universität Muenchen, Garching D-85748, Germany
²⁰ Departamento de Fisica Teorica, Universidad Autonoma de Madrid, Madrid 28049, Spain
²¹ DSM/IRFU/SPhN, CEA Saclay, Gif-sur-Yvette F-91191, France

^a Corresponding author: marcus.scheck@uws.ac.uk

Published online: 28 May 2015

Abstract

The IS475 collaboration conducted Coulomb-excitation experiments with post-accelerated radioactive ²²⁰Rn and ²²⁴Ra beams at the REX-ISOLDE facility. The beam particles (E_beam: 2.83 MeV/u) were Coulomb excited using ⁶⁰Ni, ¹¹⁴Cd, and ¹²⁰Sn scattering targets. De-excitation γ-rays were detected employing the Miniball array and scattered particles were detected in a silicon detector. Exploiting the Coulomb-excitation code GOSIA for each nucleus several matrix elements could be obtained from the measured γ-ray yields. The extracted ‹3⁻||E3||0⁺› matrix element allows for the conclusion that, while ²²⁰Rn represents an octupole vibrational system, ²²⁴Ra has already substantial octupole correlations in its ground state. This finding has implications for the search of CP-violating Schiff moments in the atomic systems of the adjacent odd-mass nuclei.