Parity-doublet structure in the $_{57}^{147}\mathrm{La}_{90}$ nucleus

Excited states in La147, populated in spontaneous fission of Cf252, have been reinvestigated by means of γ-ray spectroscopy, using high-fold γ-ray coincidences measured with the Gammasphere array of Ge detectors. The 229.5-keV level, which has been assigned spin parity 9/2− in a recent evaluation, is shown to have spin parity 11/2−. Consequently, the ground state has spin parity 5/2+. Excited levels in La147 have been arranged into a parity-doublet structure, showing that at medium excitation energy the La147 nucleus may have octupole deformation. The B(E1) rates in La147, which are factor of four lower than in La145, suggest that the electric dipole moment in La147 is depressed by an extra mechanism, probably connected with the population of particular neutron orbitals.