Quadrupole and Octupole deformations with effective triaxiality in even even nuclei

In this paper, we develop a nonadiabatic collective model for even even nuclei with effective triaxial quadrupole and octupole deformations. The model describes three-dimensional quadrupole-octupole rotation coupled with axial quadrupole-octupole vibrations. The moment-of-inertia tensor depends on the angular part of the polar coordinates in the quadrupole-octupole space, the values of which are determined from the ground state of the nucleus. In this model framework, the collective states of the yrast-alternating-parity band in the lanthanides Sm-154, Gd-154,Gd-160, Dy-156 and the actinides Th-228,Th-230,Th-232 , U-230,U-232,U-236,U-238, Pu-238 are studied .