Octupole deformation in neutron-rich barium isotopes

Partial decay schemes for the very neutron-rich nuclei ${}_{}{}^{142}{}_{}{}^{}$,144Ba and ${}_{}{}^{146}{}_{}{}^{}\mathrm{Ba}$ have been determined by the study of γ-γ coincidences in ${}_{}{}^{252}{}_{}{}^{}\mathrm{Cf}$ fission fragments. Interlaced positive- and negative-parity levels connected by fast electric dipole transitions are observed in ${}_{}{}^{144}{}_{}{}^{}\mathrm{Ba}$ and ${}_{}{}^{146}{}_{}{}^{}\mathrm{Ba}$ above spin 7ħ. This is similar to the situation in some light actinide nuclei, where the data have been interpreted in terms of reflection-asymmetric shapes.