Octupole deformation for Ba isotopes in a reflection-asymmetric relativistic mean-field approach

The potential energy surfaces of even-even 142-156 Ba are investigated in the constrained reflectionasymmetric relativistic mean-field approach with parameter set PK1.It is shown that for the ground states,142Ba is near spherical,158Ba well quadrupole-deformed,and in between 144-154Ba octupole deformed.In particular,the nuclei 148,150 Ba with N=92,94 have the largest octupole deformations.By including the octupole degree of freedom,energy gaps N = 88,N = 94 and Z = 56 near Fermi surfaces for the singleparticle levels in 14SBa with β2～0.26 and β3～0.17 are found.Furthermore,the performance of the octupoledeformation driving pairs(v2f7/2,vli13/2)and(π2d5/2,π1h11/2)is demonstrated by analyzing the singleparticle levels near Fermi surfaces in 148Ba.