https://doi.org/10.1140/epjs/s11734-024-01175-6
Review
Shape isomers: status and perspectives across the nuclear chart
1
Dipartimento di Fisica, Università di Milano, 20133, Milan, Italy
2
Istituto Nazionale di Fisica Nucleare, 20133, Milan, Italy
3
Niewodniczanski Institute of Nuclear Physics PAN, Radzikowskiego 152, 31-342, Krakow, Poland
4
Horia Hulubei National Institute of Physics and Nuclear Engineering - IFIN HH, 077125, Bucharest, Romania
5
IJC Lab, CNRS/IN2P3, Université Paris-Saclay, 91406, Orsay, France
Received:
1
March
2024
Accepted:
17
April
2024
Published online:
2
May
2024
The paper reviews the searches for shape isomers, which are “extreme” example of shape-coexistence phenomena in nuclei. They may appear when highly deformed structures, well localized in the nuclear Potential Energy Surface (PES) in the deformation space, undergo a significant change in shape to match the final state shape, thus leading to a substantially hindered 
decay. This is in sharp contrast to the vast majority of shape-coexistence phenomena, where significant mixing in the initial and final state wave functions is found. So far, the most spectacular examples of shape isomerism are known in fissioning systems in the actinides, although only scarce experimental information is available from experiments conducted more than 20 years ago. Searches in lighter mass regions, guided by theory predictions based on different approaches and experimental investigations on superdeformed systems, are also presented. They point to 
Ni as additional examples of prolate deformed shape-isomer-like structures, although with much reduced hindrance with respect to the actinides. Their origin is strictly related to the action of the monopole component of the tensor force of the nucleon-nucleon interaction, which is expected to favor the appearance of deep secondary minima also in the PES of Sn nuclei with masses 112–118. Perspectives in current searches of shape isomerism with modern detection systems, in the actinides regions and in lighter masses, are discussed.
© The Author(s) 2024
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
