Stabilization of octupole deformation with angular-momentum increase in the alternating-parity bands

Abstract

Background: Low-lying octupole collective excitations play an important role in describing the structure of nuclei in different regions of the nuclide chart. Ground state alternating-parity rotational bands combining both positive- and negative-parity states are known in several nuclei. The experimental data indicate that octupole deformation becomes stable with increase of the angular momentum.Purpose: We introduce a nondimensional characteristic of the spectra of the ground state alternating-parity bands and apply it to investigation of a stabilization of the octupole deformation with increase of the angular momentum.Method: We analyze the experimental data on the energies of the states belonging to the alternating-parity bands based on the ratio of the interpolated and the experimental energies of the negative-parity states. Interpolated energies are determined by the experimental energies of the neighboring positive-parity states assuming smooth dependence on the angular momentum.Results: The values of the ratio of the interpolated and the experimental energies of the negative-parity states belonging to the ground state alternating-parity bands of ${}^{144,146}\text{Ba}$ and some rare-earth and actinide nuclei are evaluated.Conclusion: It is shown that the angular-momentum dependence of the ratio of the interpolated and the experimental energies of the negative-parity states belonging to the ground state alternating-parity bands of ${}^{144,146}\text{Ba}$ and some rare-earth and actinide nuclei indicates stabilization of the octupole deformation with angular-momentum increase.