Speaker
Description
The fission process forms highly excited fragments carrying significant amounts of angular momentum. This formation is generally described via a shape evolution on the potential energy landscape of the fissioning system. Among the aspects that are still hard to describe in this process is the generation of the fragment angular momenta, highlighted by the work of Wilhelmy et al. in the early 1970s. Isomeric yield ratios (IYR) offer the possibility to address this question.
Traditionally, gamma-spectrometry has been used to measure IYR but risk suffering from incomplete information on the nuclear level scheme and decay branching ratios. To avoid this problem, we employ direct ion counting using mass measurement techniques and unambiguously determine IYR from fission. With recent advances such as the Phase-Imaging Ion-Cyclotron-Resonance (PI-ICR) technique, isomers with mass differences as low as a few tens of keV can be resolved. Over the past years, IYR for many different isomeric pairs resulting from 232Th(p,f), 232Th(a,f), and 238U(p,f) could be obtained at IGISOL of the University of Jyväskylä [1-5].
We present the employed experimental technique, recent experimental results, interpretation of the experimental data in terms of fragment angular momenta and our planned activities.
[1] V. Rakopoulos, et al., Phys. Rev. C 98, 024612 (2018).
[1] V. Rakopoulos, et al., Phys. Rev. C 99, 014617 (2019).
[2] Z. Gao, et al., Phys. Rev. C 108, 054613 (2023).
[3] S. Cannarozzo, et al., Phys. Rev. C 111, L031601 (2025).
[4] S. Cannarozzo, et al., [https://arxiv.org/abs/2504.11274v3][1] (2025).
