Description of octupole degrees of freedom in the U(5) ↔ SO(13) transitional region

In this paper, we discuss the problem of describing the collective states with negative parity in even-even nuclei by adding f boson to the usual sd-interacting boson model. The sdf -interacting boson model, which includes monopole ($s,L=0$), quadrupole ($d,L=2$) and octupole ($f,L=3$) degrees of freedom, enables analyzing the electric transitions of atomic nuclei. We proposed a solvable extended transitional Hamiltonian based on affine SU(1,1) Lie algebra within the framework of the sdf -interacting boson model to describe the low-lying octupole states between the spherical and deformed gamma-unstable shapes. Numerical extraction to low-lying energy levels and transition probabilities within the control parameters of this evaluated Hamiltonian are presented for various N values. By reproducing the experimental results, the extended interacting boson model calculations provide a better description of Pd isotopes in this transitional region.