Microscopic description of octupole collective excitations near N=56 and N=88

Octupole deformations and related collective excitations are analyzed using the framework of nuclear density functional theory. Axially symmetric quadrupole-octupole constrained self-consistent mean-field (SCMF) calculations with a choice of universal energy density functional and a pairing interaction are performed for Xe, Ba, and Ce isotopes from proton-rich to neutron-rich regions, and neutron-rich Se, Kr, and Sr isotopes, in which enhanced octupole correlations are expected to occur. Low-energy positive- and negative-parity spectra and transition strengths are computed by solving the quadrupole-octupole collective Hamiltonian, with the inertia parameters and collective potential determined by the constrained SCMF calculations. Octupole-deformed equilibrium states are found in the potential energy surfaces of the Ba and Ce isotopes with N approximate to 56 and 88. The evolution of spectroscopic properties indicates enhanced octupole correlations in the regions corresponding to N approximate to Z approximate to 56, Z approximate to 88 and Z approximate to 56, and N approximate to 56 and Z approximate to 34. The average beta(30) deformation parameter and its fluctuation exhibit signatures of octupole shape-phase transition around N = 56 and 88.

Automated summary

The study shows the presence of octupole-deformed equilibrium states in the potential energy surfaces of Ba and Ce isotopes with N approximately equal to 56 and 88. The evolution of spectroscopic properties indicates enhanced octupole correlations in regions corresponding to N approximately equal to Z approximately equal to 56, Z approximately equal to 88, and Z approximately equal to 56, and N approximately equal to 56 and Z approximately equal to 34.