Quadrupole-octupole coupling and the onset of octupole collectivity

Octupole deformation and collective excitations are studied within the interacting boson model. By using the results of the self-consistent mean-field calculations with a universal energy density functional, the Hamiltonian of the interacting $s$, $d$, and $f$ boson system is completely determined. A global systematic study confirms that significant octupole effects are present in actinide, lanthanide, and rare-earth nuclei corresponding to particular nucleon numbers for which octupole correlations are empirically suggested to be enhanced.