Nonaxial-octupole Y_{32} correlations in N = 150 isotones from multidimensional constrained covariant density functional theories

Abstract

The non-axial reflection-asymmetric $\beta_{32}$ shape in some transfermium nuclei with N=150, namely $^{246}$Cm, $^{248}$Cf, $^{250}$Fm, and $^{252}$No are investigated with multidimensional constrained covariant density functional theories. By using the density-dependent point coupling covariant density functional theory with the parameter set DD-PC1 in the particle-hole channel, it is found that, for the ground states of $^{248}$Cf and $^{250}$Fm, the non-axial octupole deformation parameter $\beta_{32} > 0.03$ and the energy gain due to the $\beta_{32}$ distortion is larger than 300 keV. In $^{246}$Cm and $^{252}$No, shallow $\beta_{32}$ minima are found. The occurrence of the non-axial octupole $\beta_{32}$ correlations is mainly from a pair of neutron orbitals $[734]9/2$ ($\nu j_{15/2}$) and $[622]5/2$ ($\nu g_{9/2}$) which are close to the neutron Fermi surface and a pair of proton orbitals $[521]3/2$ ($\pi f_{7/2}$) and $[633]7/2$ ($\pi i_{13/2}$) which are close to the proton Fermi surface. The dependence of the non-axial octupole effects on the form of energy density functional and on the parameter set is also studied.