Impact Of Pairing Interactions On Fission In Actinide Nuclei

In this thesis,we use the deformed mean-field plus standard pairing model to investigate the role of pairing interactions on fission in actinide nuclei isotopes.The multi-dimensional potential energy surface,static fission path and fission barrier of actinide fission nuclei is de-scribed systematically.It is found that pairing interactions play a crucial role in the region of the inner and outer barriers.The barrier heights obtained by using the present model are found to reproduce the experimental data remarkably well and yield better results than those obtained by using the BCS approximation.Through numerical analysis,we provide a possible microscopic description for the spontaneous fission in the current pairing model.Firstly,this thesis introduces the background and basis of the research,gives the expression of the general Hamiltonian under the present model.A new iterative algorithm for the exact solution of the standard pairing problem is presented,based on the Richardson-Gaudin method using the polynomial approach.The pairing interaction strengths are determined by fitting the experimental values of the odd-even mass differences of^220-235Th,^222-237U,and^224-239Pu.The single-particle energies obtained from the Woods-Saxon potential(WS)approaches,the total energy is calculated by macro-micro model.Based on the current model,the multidimensional the potential energy surface,static fission paths,energy curve under different pairing interaction strength,fission barrier height curve with pairing interaction and information entropy of above the isotope chain are analyzed and the role of interaction in fission is explored.In addition,the effects of the interaction on the fission barriers are also investigated,and the fission barriers of Th,Pa,U,Np,Pu,Pu,Am,Cm,Bk,Cf isotope chains are analyzed.The results of numerical analysis indicates that pairing interaction plays different roles in different stages of the fission process on the present model:the first and second saddle points are much more sensitive to the pairing interaction strength than the ground-state and prescis-sion points,which are mainly driven by nuclear deformation,which demonstrates that pairing interactions play a crucial role in the regions of the inner and outer barriers.The systematic investigation of the inner and outer fission barriers in even-even nuclei of^220-235Th,^222-237U,and^224-239Pu isotopes shows that the“Exact”pairing model reproduces the inner and outer barrier heights considerably closer to the experimental data than those obtained by using thescheme,especially for the outer barrier heights.The above results show the reliability and validity of this model in the study of fission process.Furthermore,the theoretical analysis of information entropy and its derivatives reveal the intense competition between the deforma-tion and the pairing interaction at the inner barrier and outer barrier under the current model.For the ground-state and prescission points,the systems are more like those in the deformation dominant case and are less affected by the pairing interaction.The magnitudes of the pair-ing energies at the first and second saddle points grow faster than that at the ground-state and prescission points with the variation of the pairing interaction strength,which confirms that pairing interactions play a crucial role in the regions of the inner and outer barriers.