Several new high-spin states are observed in the prompt $\gamma$-rays emitted from the neutron-rich, odd-$Z$ ${}^{145,147}\mathrm{La}$ fragments produced in the spontaneous fission of ${}^{252}\mathrm{Cf}.$ Alternating parity bands are extended up to spins 41/2 and 43/2 in ${}^{145,147}\mathrm{La},$ respectively. A new band completes the evidence for two sets of parity doublets expected for octupole correlations. Eight $B\left(E1\mathrm{}\right)/B\left(E2\mathrm{}\right)\mathrm{}$ ratios (four new) between two bands in ${}^{145}\mathrm{La}$ are all essentially constant and somewhat larger than similar ratios in ${}^{143,144}\mathrm{Ba},$ where stable octupole deformation and/or correlations are reported. The new ratios out of the ${31/2}^{-}$ levels in both nuclei show a sharp spike compared to other states, presumably from a strong reduction in $E2\mathrm{}$ strengths in this backbending region. In ${}^{145}\mathrm{La},$ collective bands show competition and coexistence between symmetric and asymmetric shapes. Band crossings occur in both nuclei around $ħ\omega \approx 0.26–0.30\hspace{0.5em}\mathrm{MeV}.$ Their backbends are associated with the alignment of two $i_{13/2}$ neutrons according to cranked shell model calculations.

• Received 6 July 1998

DOI:https://doi.org/10.1103/PhysRevC.59.1316