Impact Of Triaxiality On The Outer Fission Barriers Of Actinide Nuclei

Since the discovery of fission,the research of the nuclei fission barrier has always been the focus of nuclear study.As one of the basic information of nuclear fission,the fission barrier plays important roles both in theory and practice.On the one hand,the height of the fission barrier is a measure for the stability of a nucleus reflected in the spontaneous fission lifetimes of these nuclei;On the other hand,the actinide nuclei are the main basis of current nuclear energy application.Detailed information about the fission barriers helps to understand the nuclear technology and to ensure that nuclear technology is used safely and effectively.Based on the Skyrme energy density functional theory,this work selects UNEDF1 to calculate the total energy in the hartree-fock-Bogoliubov mean-field adopts self-consistency.We picture the nuclear fission process as an evolution of the nuclear shape.The coordinates of the optimal fission path in the collective space corresponds to minimal energy.By comparing the energy of several deformation parameters(?),a stepping scheme is finally selected for the optimized basis.The continuity and convergence of the results are also verified by calculating with other schemes.The fission barrier of 240 Pu is calculated on the optimized basis,and we can see that further removal of the constraint on the triaxial degree of freedom value lowers the inner barrier by about 3 Me V.A small decrease(a few hundred ke V)in energy for the second fission barrier due to the additional inclusion of the triaxial degree of freedom.These results are more consistent with the experimental data.In addition,we construct an interpolation function based on Taylor's formula to obtain a smooth potential surface.The most possible fission trajectory can be obtained by random walking on this surface.By extending the barrier calculation to actinides,it is generally concluded that the triaxial deformation can reduce the height of the outer barrier,which is positively correlated with the number of nucleons.When triaxial degrees of freedom are minimized,the values of triaxial and octupole degrees of freedom have a dramatic change at the barrier area,which is also proportional to the number of nucleons.In addition,pairing energy and other degrees of freedom are also affected by triaxial deformations.