Abstract: Beta-delayed fission (βDF) is a process, in which an excited state populated via β decay undergoes fission. The achievable excitation energy is limited by Qβ value of parent nucleus, which is usually around 10 MeV or less. Thus, βDF belongs to so called low-energy fission, which is sensitive to structure of the nucleus. This phenomenon opens new possibilities to study fission properties of exotic isotopes (such as probability of βDF, fission fragment mass distributions, fission barriers) for which other approaches to low-energy fission research would be extremely difficult or currently impossible. Moreover, βDF is important for yields of isotopes in the nucleosynthesis r-process, where alongside spontaneous and neutron-induced fission it is responsible for its termination and for fission recycling.
Presently, two regions of the nuclear chart with occurrence of βDF are readily accessible and are investigated by the modern experimental techniques: neutron-deficient region between thallium and francium, and neutron-deficient actinides. While the former region can be accessed both by the ISOL techniques with use of mass separation and by the complete-fusion reactions coupled to recoil separators, the latter region can be explored only by the complete-fusion experiments.
In this seminar, βDF process and its importance will be introduced. An overview of experimental results from the last decade will follow, showing examples from both regions of nuclei and both experimental techniques. Future possibilities for further βDF investigations in these regions of isotopes and plans to initiate experiments in the neutron-rich nuclei near francium will be discussed as well.