Medium- and high-spin band structure of the chiral-candidate nucleus ${}^{134}$Pr

Medium- and high-spin states of ${}^{134}$Pr were populated using the ${}^{116}$Cd(${}^{23}\text{Na},5n$) reaction and studied with the GAMMASPHERE spectrometer. Several new bands have been found in this nucleus, one of them being linked to the previously observed chiral-candidate twin-band structure. The ground state of ${}^{134}$Pr could be determined through establishing a level structure that connects the two previously known long-lived isomeric states. Unambiguous spin-parity assignments for the excited states could be performed based on the known 2${}^{-}$ spin-parity of the ground state combined with the present experimental data. Intrinsic single-particle configurations have been assigned to the newly observed bands on the basis of the measured $B\left(M1\right)/B\left(E2\right)$ ratios, alignments, band-crossing frequencies, bandhead spins, the observed single-particle configurations in the neighboring nuclei, and taking into account the predictions of total Routhian surface and tilted-axis cranking calculations.

Figure 1

Typical $\gamma \gamma \gamma$-coincidence spectra obtained in the present work. In panel (a) the double gate was set on band 12 transitions. Peaks labeled with full circles, full upward triangles, and full downward triangles belong to bands 12, 11, and 13, respectively, while peaks labeled with open circles and open squares belong to bands 5 and 6, respectively. In panel (b) the double gate was set on band 10 transitions. Peaks labeled with full circles, open circles, and open squares belong to bands 10, 5, and 6, respectively. In panel (c) the double gate was set on band 6 transitions. Peaks labeled with full circles, full squares, full upward triangle, and full downward triangles belong to bands 6, 12, 10, and 11, respectively, while peaks labeled with open circles belong to band 1. Peaks labeled with stars in all the panels belong to transitions between bands.

Figure 2

Low- and medium-spin negative-parity bands of ${}^{134}$Pr obtained in the present work. Linking transitions to the rest of the level scheme are plotted in the left side of the figure. The energies are given in keV, while the widths of the transitions are proportional to their relative intensities.

Figure 3

Positive-parity bands of ${}^{134}$Pr obtained in the present work. The energies are given in keV, while the widths of the transitions are proportional to their relative intensities.

Figure 4

High-spin negative-parity bands of ${}^{134}$Pr obtained in the present work. In order to show the decays out to the positive-parity bands some levels of these bands are plotted by thick lines; however, the decays between these positive-parity levels are not plotted in this figure. The decays out to the negative-parity medium-spin bands are indicated in Fig. 2. The energies are given in keV, and the widths of the transitions are proportional to their relative intensities.

Figure 5

Experimental $B\left(M1\right)/B\left(E2\right)$ ratios of the ${}^{134}$Pr bands obtained in the present work compared with calculated values assuming different configurations.

Figure 6

Alignments (a) and Routhians (b) of the bands observed in the present experiment as a function of the rotational frequency. Experimental points connected by solid (dashed) lines correspond to the even-spin (odd-spin) branch of the band.

Figure 7

Observed signature splittings for the three positive-parity $\Delta I=1$ bands.

Figure 8

Comparison of the experimental Routhians ($E^{\prime }$) and aligned angular momenta ($I_x$) of the two-quasiparticle negative-parity bands with that predicted by the TRS calculations for the lowest-lying negative-parity configurations.