Octupole degree of freedom for nuclei near 152Sm in a reflection-asymmetric relativistic mean-field approach

The potential energy surfaces of even-even isotopes near 152Sm are investigated within the constrained reflection-asymmetric relativistic mean-field approach using parameter sets PK1 and NL3. It is shown that the critical-point candidate nucleus 152Sm marks the shape/phase transition not only from U(5) to SU(3) symmetry, but also from the octupole deformed ground state in 150Sm to the quadrupole deformed ground state in 154Sm. The important role of the octupole deformation driving pair (ν2f7/2, ν1i13/2) is demonstrated based on the components of the single-particle levels near the Fermi surface. In addition, the patterns of both the proton and the neutron octupole deformation driving pairs (ν2f7/2, ν1i13/2) and (π2d5/2, π1h11/2) are investigated.