The level structures of ${}_{}{}^{143}{}_{}{}^{}\mathrm{Ba}$ and ${}_{}{}^{147}{}_{}{}^{}\mathrm{Ce}$ have been investigated by studying the β decays of 1.8-s ${}_{}{}^{143}{}_{}{}^{}\mathrm{Cs}$ and 4.1-s ${}_{}{}^{147}{}_{}{}^{}\mathrm{La}$ to search for evidence of intrinsic reflection asymmetry in light rare-earth nuclei. Gamma-ray energies and relative intensity values, γ-γ coincidence intensities, and γ-γ angular correlation coefficients were measured. The parity doublets that characterize reflection asymmetric rotational structures in the light odd-A actinides were not readily identified in ${}_{}{}^{143}{}_{}{}^{}\mathrm{Ba}$ or ${}_{}{}^{147}{}_{}{}^{}\mathrm{Ce}$. The observed level structures, combined with other data for these nuclides, suggest that weak deformation is present and that reflection asymmetric admixtures may play a significant role in driving that deformation.

• Received 5 July 1989

DOI:https://doi.org/10.1103/PhysRevC.40.2804