In-beam spectroscopy of medium- and high-spin states in ${}^{133}\mathrm{Ce}$

Medium and high-spin states in ${}^{133}\mathrm{Ce}$ were investigated using the ${}^{116}\mathrm{Cd}$(${}^{22}\mathrm{Ne}, 5n$) reaction and the Gammasphere array. The level scheme was extended up to an excitation energy of $\sim 22.8$ MeV and spin 93/2 $\hslash$. Eleven bands of quadrupole transitions and two new dipole bands are identified. The connections to low-lying states of the previously known, high-spin triaxial bands were firmly established, thus fixing the excitation energy and, in many cases, the spin parity of the levels. Based on comparisons with cranked Nilsson-Strutinsky calculations and tilted axis cranking covariant density functional theory, it is shown that all observed bands are characterized by pronounced triaxiality. Competing multiquasiparticle configurations are found to contribute to a rich variety of collective phenomena in this nucleus.

Figure 1

Part 1 of the level scheme of ${}^{133}\mathrm{Ce}$. The widths of the arrows are proportional to the relative intensities of the $\gamma$ rays.

Figure 2

Part 2 of the level scheme of ${}^{133}\mathrm{Ce}$. The widths of the arrows are proportional to the relative intensities of the $\gamma$ rays. The intensities of the $Q$ bands are given as a percentage relative to that of the yrast band $D2$.

Figure 3

Representative double-gated coincidence spectra for bands $D8$ and $D9$ in ${}^{133}\mathrm{Ce}$. The gates were placed on selected transitions in each sequence and are indicated. The transitions marked with asterisks represent the members of the band, while those marked with # are identified contaminants from other bands.

Figure 4

Representative double-gated coincidence spectra for bands $Q1, Q2$, and $Q3$ in ${}^{133}\mathrm{Ce}$. The gates were placed on selected transitions in each band. Transitions marked with asterisks represent the band members, while those marked with # are identified contaminants from other bands.

Figure 5

Representative double-gated coincidence spectra for bands $Q4, Q5$, and $Q6$ in ${}^{133}\mathrm{Ce}$. The gates were set on selected transitions in each band. The transitions marked with asterisks represent the band members, while those marked with # are identified contaminants from other bands.

Figure 6

Representative double-gated coincidence spectra for bands $Q7, Q8, Q9, Q10$, and $Q11$ in ${}^{133}\mathrm{Ce}$. The gates were set on selected transitions in each band. The transitions marked with asterisks represent the band members, while those marked with # are identified contaminants from other bands.

Figure 7

Energies relative to a standard rotating liquid drop reference calculated for the experimental bands observed in ${}^{133}\mathrm{Ce}$. The Harris parameters used are ${\mathcal{J}}_0=22{\hslash }^2 {\text{MeV}}^{-1}$ and ${\mathcal{J}}_1=11{\hslash }^4$ ${\text{MeV}}^{-3}$.

Figure 8

(a) Experimental alignments for bands $D2, D3, D6, D8$, and $D9$. (b) Experimental alignments for bands $Q2$–$Q10$. The Harris parameters used to obtain these plots are ${\mathcal{J}}_0=22{\hslash }^2 {\text{MeV}}^{-1}$ and ${\mathcal{J}}_1=11{\hslash }^4 {\text{MeV}}^{-3}$.

Figure 9

The observed bands $D3, D6, D8$, and $D9$ of ${}^{133}\mathrm{Ce}$ are shown relative to a rotating liquid drop reference in the upper panel, with the calculated configurations assigned to these bands shown relative to the same reference in the middle panel. The lower panel shows the difference between calculations and experiment.

Figure 10

The observed bands $Q2$–$Q10$ of ${}^{133}\mathrm{Ce}$ are provided relative to a rotating liquid drop reference (upper panel), and the corresponding calculated configurations are displayed relative to the same reference (middle panel). The difference between calculations and experiment are provided at the bottom. The same $[7_{-}{1}_{-},{43}_{-}\left(00\right)]$ configuration is assigned to bands $Q2$ and $Q3$, but with different triaxial deformation (see text). As the minima are very close in energy, only one curve is calculated and presented in the middle panel for this configuration.

Figure 11

Calculated energy spectrum (upper panel) and frequency spectrum (lower panel) as a function of spin together with the data on band $D3$.