Speaker
Description
The neutron-rich rare-earth nuclei in the A$\sim$160 mass region lie in one of the deformed sectors of the nuclear chart. Examining these nuclei helps us understand the evolution of nuclear deformation. The systematics of the first excited $2^+$ states in even-even nuclei suggest that Nd ($Z=60$) isotopes exhibit among the largest ground-state deformations in the A$\sim$160 region. Experimental data near such nuclei in the far-from-stability regime have been limited, but advances in radioactive-beam facilities have made their study accessible. $\beta$-$\gamma$ spectroscopy serves as an important probe to study the nuclear structure. These studies are of astrophysical importance for understanding the origin of the rare-earth peak in the abundance distribution of the rapid neutron-capture process of nucleosynthesis, a feature thought to arise from the combined effects of maximum in nuclear deformation and $\beta$-decay. In this work, we investigate the $\beta$-$\gamma$ spectroscopy of $^{156}$Pr ($Z=59$, $N=97$) to populate its daughter $^{156}$Nd ($Z=60$, $N=96$).
The experiment was conducted at RIBF, RIKEN, using in-flight fission of a 345 MeV/nucleon $^{238}$U beam on a Be target to produce neutron-rich rare-earth isotopes. The isotopes were separated and identified using the BigRIPS separator. An active stopper, WAS3ABi, was used for ion- and $\beta$-detection, while an array of Ge detectors, EURICA, was used for $\gamma$-ray detection. This enabled us to perform the $\beta$-$\gamma$ spectroscopy.
In the presentation, first $\beta$-$\gamma$ decay spectroscopy results for $^{156}$Pr will be presented, providing nuclear structure information relevant to rare-earth peak formation.