Speaker
Description
The $\beta$-decay study of indium-133 provides a unique connection between nuclear structure and astrophysics. On one hand, $^{133}$In is a perfect $\beta$-decay demonstrator of r-process nuclei in the vicinity of $N=82$ owing to its extreme neutron-proton asymmetry and thus large $Q_{\beta}$ and $Q_{\beta n}$ windows. On the other hand, its decay daughter, $^{133}$Sn, is simple in its nuclear structure due to the proximity to the doubly magic $^{132}$Sn. Thus, a measurement on the $\beta$-strength function of $^{133}$In allows us to unravel how the r-process nuclei decay, benchmarking the state-of-the-art nuclear models with a simple representation. This is extremely crucial for the nuclear models in assessing their prediction power in more exotic regions that are out of experimental reach.
We did the experiment at the ISOLDE decay station (IDS). The neutron time-of-flight array, INDIe [1-3], was installed at IDS to measure neutron spectroscopy from $^{133}$Sn following the $^{133}$In $\beta$ decay. Several strong and isolated neutron resonances were observed below Ex=6 MeV, including the previously observed state at Ex=3.56 MeV [4-6]. More importantly, we quantified for the first time the single GT strength of the $\nu g7/2\rightarrow\pi g9/2$ transformation which dominates the $\beta$ decay of a large number of exotic nuclei to the southeast of $^{132}$Sn. In this contribution, we will present our latest results regarding the excitation energies, branching ratios, and log$ft$ of a series of neutron unbound states newly observed in the $^{133}$In decay. Our experimental findings were compared to the large-scale shell-model calculations employing several different effective interactions. The result suggests the proton excitation across $Z=50$ plays an important role to understand quantitatively the GT strength measured in this work.
[1] W.A. Peters et al., Nucl. Inst. Meth. A 836, 122 (2016).
[2] S.V. Paulauskas et al., Nucl. Inst. Meth. A 737, 22 (2014).
[3] R. Lica et al., in preparation.
[4] P. Hoff et al., Phys. Rev. Lett. 77, 1020 (1996).
[5] V. Vaquero et al., Phys. Rev. Lett. 118, 202502 (2017).
[6] M. Piersa et al., Phys. Rev. C 99, 024304 (2019).
