原子能科学技术 ›› 2022, Vol. 56 ›› Issue (5): 888-895.DOI: 10.7538/yzk.2022.youxian.0250

• 核数据模型理论与评价 • 上一篇    下一篇

234U裂变的五维势能曲面计算

朱鑫;王智明;罗昶恺;倪磊;钟春来;樊铁栓   

  1. 集美大学 理学院,福建 厦门361021;北京大学 物理学院 重离子研究所 核物理与核技术国家重点实验室,北京100871
  • 出版日期:2022-05-20 发布日期:2022-05-20

Macro-microscopic Calculation of Five-dimensional Potential Energy Surface for 234U Fission

ZHU Xin;WANG Zhiming;LUO Changkai;NI Lei;ZHONG Chunlai;FAN Tieshuan   

  1. School of Science, Jimei University, Xiamen 361021, China;State Key Laboratory of Nuclear Physics and Technology, Institute for Heavy Ion Physics, School of Physics, Peking University, Beijing 100871, China
  • Online:2022-05-20 Published:2022-05-20

摘要: 本工作基于连接二次曲面的形状描述+LSD(LublinStrasbourg drop)公式+折叠汤川势建立了宏观微观模型。对234U裂变,计算了具有5 906 250个格点的五维势能曲面,然后通过搜索势能曲面得到了对称裂变和非对称裂变两个裂变通道,给出了裂变势垒高度以及鞍点和断点等特殊位置的原子核形状。

关键词: 宏观-微观模型, 势垒高度, 鞍点, 五维势能曲面

Abstract: A key question about the fission process of a heavy nucleus is to probe the nuclear potential energy landscape and its evolution from the single groundstate compound nucleus over the top of the fission barrier and further to the scission point, finally terminating in the formation of fission fragments. In this work, a macromicroscopic model was established to calculate the fission properties for uranium elements. The total potential energy as a function of deformation parameters was divided into a smoothly varying macroscopic part and a microscopic part representing quantum effect correction. The nuclear shape was described by the SwiateckiNix threequadraticsurface (3QS) parametrization, which could accurately represent the nuclear shape evolution all the way from the ground state to the scission configuration. The macroscopic part of the nuclear potential energy was calculated by the LSD (LublinStrasbourg drop) model. In the microscopic part, the foldedYukawa potential was used as the independent particle potential, whereas the shell correction method of Strutinsky and the smooth BCS pairing model were used to calculate the deformation energy of the compound nucleus. For the 234U compound nucleus, a potential energy surface (PES) with 5 906 250 lattice points was calculated and analyzed in a fivedimensional deformation space given by the 3QS parametrization. The watershed algorithm was used to search the fission paths on the fivedimensional PES for 234U. For different nuclear shapes, there are two well separated fission paths, asymmetric and symmetric, which share the same inner barrier and deviate at the point of second minimum, and finally end at two different points of the PES. During reaching scission points, the asymmetric fission pass will cross a new barrier with lower height than the outer barrier, but the height of the new barrier needs to be crossed is higher than the outer barrier for the symmetric fission path. The heights of fission potential barrier and the nuclear shapes at special positions, such as the saddle point and the scission point, were given for 234U. The comparison of our results, the inner barrier height and outer barrier height, with available experimental data and other’s theoretical results confirms the reliability of our calculations. The calculated results of this work, especially the outer barrier in the large deformation area, are in good agreement with the experimental data of RIPL library and Moller’s calculation, which means that the 3QS parametrization might be closer to the real nuclear shape than the generalized Lawrence shape description specially in the large deformation region.

Key words: macro-microscopic model, barrier height, saddle point, five-dimensional potential energy surface