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Description
Octupole correlations in barium isotopes have been experimentally reported up to $N$=90 [1,2], with more recent evidence suggesting that this behaviour may persist up to $N$=94 [3]. The same study, together with symmetry-conserving configuration mixing (SCCM) calculations, supports an evolution toward increasingly quadrupole-deformed shapes accompanied by sustained octupole correlations in this region.
New spectroscopic information on the neutron-rich $^{148}$Ba isotope was obtained using the GRIFFIN spectrometer together with the PACES detector for internal conversion electron spectroscopy, following the $\beta$-decay of $^{148}$Cs. This research combines $\gamma$-ray and internal conversion electron (ICE) data to constrain transition multipolarities and mixing ratios. Particular attention is given to a state previously reported with a tentative $(3^-)$ assignment, whose structure is re-examined in light of the new data. The observed decay pattern supports a spin assignment of $J=3$, while the parity remains to be confirmed through internal conversion coefficient (ICC) analysis or lifetime considerations, in order to strengthen the proposed band structure.
Ongoing analysis aims to clarify the low-lying structure of $^{148}$Ba and the emerging picture of octupole collectivity. The results are discussed in the context of isotopic and isotonic systematics, providing insight into the evolution of quadrupole deformation and octupole correlations in this mass region.
\textbf{References}
[1] B.~Bucher \textit{et al.},
Phys.\ Rev.\ Lett.\ \textbf{116}, 112503 (2016).
[2] B.~Bucher \textit{et al.},
Phys.\ Rev.\ Lett.\ \textbf{118}, 152504 (2017).
[3] R.~Lică \textit{et al.},
Phys.\ Rev.\ C \textbf{97}, 024305 (2018).
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