https://doi.org/10.1140/epja/s10050-020-00071-6
Regular Article – Experimental Physics
Evidence for octupole collectivity in 
1
KTH Royal Institute of Technology, 10691, Stockholm, Sweden
2
Department of Physics, Faculty of Science, Istanbul University, Vezneciler/Fatih, 34134, Istanbul, Turkey
3
Department of Physics, Oliver Lodge Laboratory, University of Liverpool, Liverpool, L69 7ZE, United Kingdom
4
Department of Physics, University of Jyvaskyla, P.O. Box 35, 40014, Jyvaskyla, Finland
5
Institut für Kernphysik, Universität zu Köln, 50937, Cologne, Germany
6
Schuster Building, School of Physics and Astronomy, The University of Manchester, Manchester, M13 9PL, United Kingdom
7
Research Center for Nuclear Physics, Osaka University, Osaka, 567-0047, Japan
8
STFC Daresbury Laboratory, Daresbury, Warrington, WA4 4AD, United Kingdom
9
Department of Chemistry, University of Helsinki, P.O. Box 3, 00014, Helsinki, Finland
10
Department of Physics, University of Oslo, 0316, Oslo, Norway
11
CNS, University of Tokyo, Wako, 351-0198, Japan
12
Centre de Sciences Nucléaires et Sciences de la Matière, CNRS/IN2P3, Université Paris-Saclay, 91405, Orsay, France
13
Division of Cancer Sciences, School of Medical Sciences, The University of Manchester, Manchester, M13 9PL, United Kingdom
14
Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro, 35020, Legnaro, Italy
* e-mail: ertoprak@kth.se
Received:
10
October
2019
Accepted:
11
January
2020
Published online:
20
February
2020
Excited states in the extremely neutron-deficient nucleus were populated via 
and 
reactions. The level scheme has been extended up to an excitation energy of 
and tentative spin-parity assignments up to 
. Linear polarization and angular distribution measurements were used to determine the electromagnetic E1 character of the dipole transitions connecting the positive-parity ground-state band with an excited side-band, firmly establishing it as a negative-parity band. The lowest member of this negative-parity structure was firmly assigned spin-parity 
. In addition, we observed an E3 transition from this state to the ground state, providing direct evidence for octupole collectivity in . Large-scale shell model (LSSM) and total Routhian surface (TRS) calculations have been performed, supporting the interpretation of the state as a collective octupole-vibrational state.
© The Author(s), 2020
