https://doi.org/10.1051/epjconf/202532901001
Candidates for low-lying octupole isovector (mixed-symmetry) excitations
1 School of Computing, Engineering, and Physical Sciences, University of the West of Scotland, Paisley, PA1 2BE, UK
2 SUPA, Scottish Universities Physics Alliance, UK
3 Institut für Kernphysik, TU Darmstadt, D-64289 Darmstadt, Germany
4 Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, 1784 Sofia, Bulgaria
5 Wright Nuclear Structure Laboratory, Yale University, New Haven, CT 06511, USA
6 ILL, Institut Laue-Langevin, F-38042 Grenoble Cedex, France
7 LPSC, UJF Grenoble, F-38026 Grenoble Cedex, France
8 GANIL, Grand Accélérateur National d’Ions Lourds, F-14076 Caen, France
9 Institut für Kernphysik, Universität zu Köln, D-50937 Köln, Germany
10 CNRS/IN2P3, IJCLab, University Paris-Saclay, F-91405 Orsay, France
11 Faculty of Physics, University of Warsaw, PL-00-681 Warsaw, Poland
12 Department of Physics, United States Naval Academy, Annapolis, MD 21402, USA
* e-mail: marcus.scheck@uws.ac.uk
Published online: 25 June 2025
The spectroscopic properties of low-lying octupole states, previously proposed to be candidates for isovector (mixed-symmetry) states, were investigated in 95Mo(nth, γ) and 143Nd(nth, γ) thermal neutron capture reactions. The experiments used eight Clover detectors that made up the central ring of the EXILL setup and the high thermal neutron flux of the research reactor at ILL. These measurements allowed a determination of branching ratios and multipole mixing ratios for the transitions of interest connecting the isovector candidate and the lowest-lying Jπ = 3−1 state, the octupole phonon. Furthermore, for 144Nd the lifetime of the third excited 3−3 level was remeasured using the Gamma-Ray Induced Doppler-shift method to be τ = 31+10−25. While calculations in the Quasi-particle Phonon Model indicate that the 3−3 state in 144Nd remains a good candidate for an isovector state, a simple model approach indicates that for 96Mo the isovector state must be higher in energy than the proposed 3−2 candidate at 3178 keV.
© The Authors, published by EDP Sciences, 2025
This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
