${\left(h_{11/2}\right)}^2$ alignments in neutron-rich ${}^{132}\mathrm{Ba}$ with negative-parity pairs

The shell-model collective-pair truncation with negative-parity pairs is adopted to study the ${\left(h_{11/2}\right)}^2$ alignment in ${}^{132}\mathrm{Ba}$. The proton ${\left(h_{11/2}\right)}^2$-alignment state is predicted as an $E\sim 4.6$ MeV and $\tau \sim 0.5\mu \text{s}$ isomer with relatively strong $E3$ decay channels. The oblately deformed neutron ${\left(h_{11/2}\right)}^{-2}$ alignment in the yrast band and four negative-parity bands are confirmed, even though two of these negative-parity bands favor the prolate deformation, which directly manifests the $\gamma$ instability of ${}^{132}\mathrm{Ba}$.

Figure 1

Experimental (a) [2, 34] and the calculated spectrum (b), including the yrast band, $5^{-},6^{-},7^{-},8^{-}$ bands, and the ${\left(\pi h_{11/2}\right)}^2$-alignment band, which is highlighted in red.

Figure 2

$E_I-E_{I-2}$ (a), $B(E2,I\to I-2)$ (b), and $g$ factors (c), as well as the sum of $5^{-}$ and $6^{-}$ pair numbers (d), of yrast states in ${}^{132}\mathrm{Ba}$ from experiments (Exp) [34] and our calculation (Cal). The yrast ${\left(\nu h_{11/2}\right)}^2$ alignment is highlighted.

Figure 3

$E_{I+2}-E_I$ (a) and the sum of $5^{-}$ and $6^{-}$ pair numbers (b) in $5^{-}$ and $6^{-}$ bands. Abbreviations “exp” and “cal” correspond to the experimental data [34] and calculated results, respectively. The grey zone highlights the ${\left(\nu h_{11/2}\right)}^{-2}$ alignment.

Figure 4

Sum of $5^{-}$ and $6^{-}$ pair numbers in $7^{-}$ and $8^{-}$ bands. The grey zone highlights the potential ${\left(\nu h_{11/2}\right)}^{-2}$ alignment.