Signatures of enhanced octupole correlations at high spin in ${}^{136}\mathrm{Nd}$

Experimental signatures of moderately enhanced octupole correlations at high spin in ${}^{136}\mathrm{Nd}$ are indicated for the first time. The extracted dipole moments of two negative-parity bands are only two times smaller than those of the lanthanide nuclei with $N\approx 90$ which present well-established octupole correlations. Calculations using the cranked quasiparticle random phase approximation and a model of quadrupole-octupole rotations with octupole vibrations reveal the structure of the bands and the enhanced octupole correlations at high spin in ${}^{136}\mathrm{Nd}$.

Figure 1

Partial level scheme of ${}^{136}\mathrm{Nd}$ showing the bands with enhanced octupole correlations $L5$ and $L6$, and their decay via $E1$ transitions (red color) to band $L1$.

Figure 2

Spectra constructed by double gating on the transitions above and below the connecting transitions between the bands with octupole correlations $L5$ and $L6$, and the band $L1$ of ${}^{136}\mathrm{Nd}$. The connecting transitions are marked with red labels, while the contaminant transitions are marked with an asterisk. In the upper spectrum the 330-keV transition connects band D6 reported in Ref. [13] to the ${21}^{-}$ state of band $L5$, while the 662-keV peak indicates the doublet composed of the 661-keV and 663-keV transitions of band $L1$.

Figure 3

Experimental $B\left(E1\right)/B\left(E2\right)$ ratios at low and high spin of ${}^{136}\mathrm{Nd}$. Experimental intrinsic $E1$ moments of low- and high-spin states of ${}^{136}\mathrm{Nd}$, compared with those of ${}^{146}\mathrm{Nd}$ and ${}^{148}\mathrm{Nd}$.

Figure 4

Spin alignment $i_x$ of the bands $L5$, $L6$, $L1$ and the $\mathrm{GSB}$ of ${}^{136}\mathrm{Nd}$. The spin alignments of the continuation of the bands $L5$ and $L6$ at low ($N1$) and high spin ($T3$ and $T4$, respectively) are also shown. The used Harris parameters are $J_0=10{\hslash }^2{\mathrm{MeV}}^{-1}$ and $J_2=20{\hslash }^2{\mathrm{MeV}}^{-3}$.

Figure 5

Cranked QRPA calculations for ${}^{136}\mathrm{Nd}$ showing the lowest and the next-lowest negative-parity states in each signature sector. Possible band assignment is indicated in the figure.

Figure 6

QORM description of ${}^{136}\mathrm{Nd}$ APB formed by GSB up to $I=8^{+}$ and band $N1$ up to $I={13}^{-}$. See the text for the model parameters and explanation.

Figure 7

QORM description of ${}^{136}\mathrm{Nd}$ APB formed by band $L1$ from $I={10}^{+}$ to $I={22}^{+}$ and band $L5$ from $I={17}^{-}$ to $I={23}^{-}$. See the text for the model parameters and explanation.