Nuclear collective motion of heavy nuclei with axial quadrupole and octupole deformation

A quadrupole-octupole axially symmetric model is constructed for the unified description of alternate parity bands corresponding to octupole vibration or a stable deformation. The model depends on two parameters whose clear physical meaning allows a systematic description of the rotation-vibration dynamics of alternate parity bands analyzed for isotopic sequences of Ra, Th, U, and Pu nuclei. A critical point is identified in the A = 224???228 mass region of the Ra and Th nuclei marking different stages of the transition between static and dynamic octupole deformation. Model predictions are performed for energies of unobserved states of the yrast sequence and of the excited bands as well as for the E 1, E2, and E3 transition rates, which reproduce the available experimental data and exhibit a specific spin dependence for the transitional nuclei.