Mainz 2022 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 51: Structure and Dynamics of Nuclei IX

HK 51.2: Talk

Wednesday, March 30, 2022, 16:30–16:45, HK-H7

Fission isomer studies with the FRS — •Jianwei Zhao¹, Timo Dickel^1,2, Moritz P. Reiter³, Peter G. Thirolf⁴, Michiharu Wada⁵, Nazarena Tortorelli^4,1, and Ziga Brencic⁶ for the S530 collaboration — ¹GSI, Darmstadt, Germany — ²JLU Gießen, Gießen, Germany — ³University of Edinburgh, Edinburgh, UK — ⁴LMU Munich, Munich, Germany — ⁵Wako Nuclear Science Center, Saitama, Japan — ⁶University of Ljubljana, Ljubljana, Slovenia

Multi-humped fission barriers as they occur in the actinide region give rise to isomeric fission. Such barrier shapes can be described as the result of superimposing microscopic shell corrections to the macroscopic liquid drop barrier. A whole ’island’ of fission isomers has been identified in the actinide region (Z = 92 - 97, N = 141- 151) with presently 35 experimentally observed fission isomers. Half-lives range from 5 ps to 14 ms. We will present the results of fission isomer studies with the FRS at GSI. For the first time, the fragmentation of 1 GeV/u ²³⁸U projectiles, instead of so-far used light-particle induced reactions, was employed to study fission isomers. The projectile fragmentation gives access to isotopes hard or impossible to reach by light particle reactions and the in-flight separation with FRS allows studying fission isomers with short half-lives. Most importantly, it provides beam with a high purity and with the event-by-event identification. Two detection methods were used to cover fission isomers with half-lives in the range of about 50 ns to 50 ms: beam implantation in a fast plastic scintillator and in a cryogenic stopping cell at the FRS Ion Catcher.