The decay of indium-133 at ISOLDE decay station

In this contribution, I will present an experimental work studying the beta decays of ¹³³In at the ISOLDE decay station (IDS). Uniquely to r-process nuclei, nuclear beta decay with extreme neutron excess involves neutrons and protons in different major shells of opposite parity, dividing the decay strength between forbidden, at low energies, and Gamow-Teller (GT) transitions, mostly above neutron separation energies [1]. The new neutron time-of-flight array, INDIe [2-4], was installed at IDS to investigate the neutron unbound states in ¹³³Sn populated in the beta decay of ¹³³In. Several strong transitions were observed below Ex=6 MeV, including the previously observed state at Ex=3.56 MeV [5-7]. This observation allows us to quantify with high precision the strength distribution of the GT and FF transitions in the region to the southeast of ¹³²Sn. In addition, we were able to map decay strength up to about 10 MeV excitation energy in ¹³³Sn, which is crucial to quantify multi-neutron emission probabilities in this region. Our experimental findings were compared to the theoretical predictions. We carried out large-scale shell-model calculations involving several different effective nucleon-nucleon potentials. The results of these calculations will also be discussed.