Research On The Nuclear Octupole Deformation And Fission In Reflection Asymmetric Relativistic Mean Field Theory

In the paper, we have sketched the theoretical framework of the Reflection Asymmetric Relativistic Mean Field (RAS-RMF) theory and introduced the numerical techniques to solve the relativistic equations of motion. By using the theoretical approach, we have presented a systemic investigation on the properties for 142,144,146Ba,146Ce and Ra isotopes, together with the 256,258Fm and 226Th nuclei.We have applied RAS-RMF theory to investigate the properties of ground states and shape evolution for 142,144,146Ba,146Ce,Ra isotopes.The calculated binding energies and deformations are excellently consistent with experimental data. The neutron (proton) density distributions clearly show the evolution of deformation for 142,144,146Ba,146Ce and Ra isotopes,and the asymmetric structure for 146Ba和146Ce. In particular, RAS-RMF theory provides the neutron and proton densities which show clearly the shape evolution of these nuclei from nearly spherical to well-developed octupole and finally back to quadrupole deformation shapes. This is in accordance with experimental observation. The RAS-RMF theory predicts 146Ba and 146Ce are octupole deformed nuclei, which is in acordance with the experimental data.We have studied the fission of 256,258Fm and 226Th, and presented the potential energy surface varying with the quadruple deformations and hexadecapole deformations. We have also demonstrated the process of the symmetric fission for 258Fm and 226Th nuclei, which agree the experimental observation as well as the other theoretical predictions.