Vibrational-rotational spectra of even-even nuclei with quadrupole and octupole deformations

Vibrational-rotation levels of the yrast and first nonyrast alternating-parity bands of the lanthanide Nd-150, Sm-154, Gd-154,Gd-160, Er-162,Er-164 and actinide Th-228,Th-232, U-230,U-236,U-238, Pu-240 nuclei are studied in the framework of a nonadiabatic collective model of even-even nuclei with quadrupole and octupole deformations. The theoretical spectra are obtained through the use of Gauss and harmonic-oscillator (HO) potentials in the radial part of the Schrodinger equation which is taken in polar coordinates. The change of the surface deformation of the nucleus with the collective excitation energy is taken into account. The Delta I = 1 staggering structure of the yrast alternating-parity bands is also considered. The theoretically obtained energy bands and staggering diagrams are in good agreement with the corresponding experimental data and point out the soft character of the collective quadrupole octupole deformation mode manifesting in these nuclei.