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Abstract
Atomic nuclei with certain combinations of proton and neutron numbers can adopt reflection-asymmetric or octupole-deformed shapes at low excitation energy. These nuclei present a promising avenue in the search for a permanent atomic electric dipole moment—the existence of which has implications for physics beyond the Standard Model of particle physics. Theoretical studies have suggested that certain thorium isotopes may have large octupole deformation. However, due to experimental challenges, the extent of the octupole collectivity in the low-energy states in these thorium nuclei has not yet been demonstrated. Here, we report measurements of the lifetimes of low-energy states in 228Th (Z = 90) with a direct electronic fast-timing technique, the mirror symmetric centroid difference method. From lifetime measurements of the low-lying Jπ = 1− and Jπ = 3− states, the E1 transition probability rates and the intrinsic dipole moment are determined. The results are in agreement with those of previous theoretical calculations, allowing us to estimate the extent of the octupole deformation of 228Th. This study indicates that the nuclei 229Th and 229Pa (Z = 91) may be good candidates for the search for a permanent atomic electric dipole moment.
Original language | English |
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Pages (from-to) | 853-856 |
Number of pages | 4 |
Journal | Nature Physics |
Volume | 16 |
Issue number | 8 |
Early online date | 18 May 2020 |
DOIs | |
Publication status | Published - 31 Aug 2020 |
Keywords
- octupole-deformed shapes
- pear-shaped nucleus
- MSCD
- 228Th
- mirror symmetric centroid difference method
- fast-timing technique
- experimental nuclear physics
Profiles
Projects
- 1 Finished
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Lab in a bubble
Jaroszynski, D., Boyd, M., Brunetti, E., Ersfeld, B., Hidding, B., McKenna, P., Noble, A., Sheng, Z., Vieux, G., Welsh, G. H. & Wiggins, M.
EPSRC (Engineering and Physical Sciences Research Council)
1/04/16 → 31/03/21
Project: Research