Analytical description of the excited state phase transition to octupole deformed shape in alternating parity bands

Angular momentum dependences of the parity splitting and eletric dipole transitons in the alternating parity bands of heavy nuclei have been analyzed. It is shown that these dependences can be treated in a universal way with use of a single parameter of critical angular momentum, which characterizes phase transition from octupole vibrations to the stable octupole deformation. Using the simple model of axially-symmetric reflection-asymmetric mode, the analytical expression for the partiy splitting and electic dipole transitional moment have been obtained. The results obtained are compared with the experimental data for various isotopes of Ra, Th, U, and Pu.