Exotic Nonaxial-Octupole Shapes in N=184 Isotones from Covariant Density Functional Theories

The nonaxial octupole shape in some nuclei with N = 184, namely, 284Fm, 286No, 288Rf, and 290Sg, is investigated using covariant density functional theories. Employing the density -dependent point -coupling covariant density functional theory with the parameter set DD-PC1 in the particle -hole channel, it is found that the ground states of 284Fm, 286No, 288Rf, and 290Sg have pure nonaxial octupole shapes with deformation parameters beta 31 approximate to 0.08 and beta 33 approximate to -0.01 to -0.03. The energy gain due to the beta 31 and beta 33 distortion is approximate to 1 MeV. The occurrence of the nonaxial octupole correlations is mainly from the proton orbitals 1i13/2 and 2 f7/2, which are close to the proton Fermi surface. The dependence of the nonaxial octupole effects on the form of the energy density functional and on the parameter set is also studied.