235U中子诱发裂变中基态与第一同质异能素势阱内的大振幅集体运动与耗散
Large Amplitude Collective Motion and Dissipation in the Ground State and the First Isomeric Wells in the Neutron-Induced Fission of $^{235}$U
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中文总结 AI 辅助
本研究采用时间依赖密度泛函理论，探究235U中子诱发裂变的基态与第一同质异能素势阱内的大振幅集体运动与耗散，发现两势阱动力学均具强耗散性，且质量不对称度演化特征不同，两势阱均有低概率中子发射。
中文摘要 AI 辅助
在低能中子诱发的裂变中，母核在基态与同质异能素势阱中度过了相当长的时间，最终越过外势垒，而初级裂变碎片的性质正是在此处确定。尽管如此，此前尚未用微观模型研究这两个早期阶段的动力学。本研究采用已用于处理235U(n,f)反应裂变从鞍点到断点阶段的时间依赖密度泛函理论，分别考察母核在两个势阱中的演化。裂变的这两个早期阶段是复合核形成与演化最终理论的关键组成部分。本研究表明，两个势阱内的动力学均具有强耗散性，与从鞍点到断点的动力学类似。研究还揭示，系统初始质量不对称度在基态势阱中很快收敛到极小波动，而在同质异能素势阱中，质量不对称度则以相当大的振幅做近乎简谐运动的振荡。此外，两个势阱中均有低概率的中子发射现象。
英文摘要
In fission induced by low energy neutrons, the mother nucleus spends a significant fraction of the time in the ground state and isomer wells, eventually passing beyond the outer barrier, where the primary fission fragments properties are defined. Despite this, the dynamics of these two early stages have not been investigated using microscopic models. This study examines the evolution of the mother nucleus in both wells separately, using time-dependent density functional theory, which has been previously used to treat the saddle-to-scission stage of fission for $^{235}$U(n,f) reactions. These two early stages of fission are essential blocks in the final theory of the formation and evolution of a compound nucleus. The present study shows that the dynamics in both wells is strongly dissipative, similar to the dynamics from saddle to scission. It also reveals that while the initial mass asymmetry of the system quickly settles to very small fluctuations in the ground state well, in the isomeric well, the mass asymmetry oscillates with a rather large amplitude, in almost harmonic motion. Furthermore, with low probability, neutrons are emitted in both wells.
