Description Of The Synthesis Of Superheavy Nuclei By The Two-step Model

The synthesis of superheavy nuclei is an important problem in nuclear physics.It has very important meaning on the expansion of new material,the study of nuclear properties,and the verification of nuclear theory.However the fusion theory for low heavy ions reactions is not commonly accepted,the fusion mechanism has several different explanations,therefore the prediction of the residue cross section of superheavy nuclei is not accurate.Based on the two-step model,the thesis studies the effect of shell correction energy on the heavy ion reactions,and re-calculates the residue cross sections for reactions Ca+Bk.The main works and results of the thesis are listed below:1.The temperature-dependent shell correction energy is involved in the potential surface,and the border between fusion hindered and not-fusion hindered reactions for different mass asymmetry parameter ? are analyzed.The results show that the border with consideration of shell effect is much more complicated than the case without shell effect,and show strong relations with excitation energy.2.Because the height of inner barrier has much effect on the fusion cross section,the thesis analyzed the height of inner barrier for different combinations of projectile and target.The results show such a tendency that for the same ?,the larger mass number,the higher inner barrier;for the same compound nucleus the smaller ?,the higher inner barrier,but withsome exceptions for some certain compound nucleus.3.With the consideration of liquid drop energy and shell correction energy,the reactions Ca+Bk to synthesize superheavy element Z=117 are re-calculated,and corresponding results are compared with the residue cross section with only liquid drop model.It shows that the shell effect slightly reduces the residue cross section for the reactions Ca+Bk.As a summary,through the studies,the present thesis discovered the effect of the shell correction energy on the fusion process and the residue cross sections of superheavy nuclei,and one has more understanding of the fusion mechanism of super heavy nucleus.