FLUCTUATION-DISSIPATION DYNAMICS OF FUSIOIN REACTION IN SUPERHEAVY MASS REGION AND MULTI-MODAL FISSION REACTION

我们在涨落耗散动力学的基础上研究了超重质量区的聚变反应和锕系区的多模态裂变反应。本文用多维Langevin方程进行了数值计算，用四维Langevin方程研究了两离子接触后超重核的形成。指出了颈自由度在接触早期的重要性，因为它具有很小的惯性。我们研究了核摩擦系数对碎片质量和动能分布的影响。指出了在推导核摩擦系数时，同时拟合多个物理量的重要性，并在考虑形变和取向的情况下，计算了临近相的俘获几率.指出在研究核聚变过程时，需要重新考虑在深部非弹性碰撞中确定的表面摩擦力的初始强度.我们研究了Langevin方程作为随机微分方程的性质.在随机积分中，有几种解释随机积分的方法，例如Ito积分和Stratonovich积分。比较了两种解释下的聚变和裂变过程的数值结果，并对丰中子核的裂变势垒进行了系统的研究。我们将其应用于r过程核合成中元素丰度的估计。我们指出了质量不对称裂变过程的重要性。在裂变过程发生的锕系元素区域，质量非对称裂变占主导地位，质量分配基本上是由势能面上的壳修正决定的。

We have studied the fusion reaction in superheavy mass region and the multi-modal fission reaction in actinide region on the basis of the fluctuation-dissipation dynamics. A multi-dimensional Langevin equation has been used for numerical calculations.The four-dimensional Langevin equation is used to study the formation of superheavy nuclei after the contact of two ions. We pointed out the importance of the neck degree of freedom in the very early stage of the contact, because it has very small inertia.We have studied the multi-modal fission of actinide nuclei. We have examined the effect of the nuclear friction coefficient in the mass and kinetic energy distribution of the fragments. We pointed out that it is important to fit several physical quantities at the same time when we derive the nuclear friction coefficient.For the approaching phase, we have calculated the capture probability taking into account of the deformation and the orientation of the two ions. We pointed out that the original strength of the surface friction that was determined in deep inelastic collision may need to be reexamined for the study of the fusion process.We have studied the properties of the Langevin equation as a stochastic differential equation (SDE). In the integration of SDE, there are several ways of interpreting the stochastic integrals, for example Ito integral and Stratonovich integral. We compared the numerical results for fusion and fission process with two interpretations.We have also performed the systematic study of the fission barrier for neutron-rich nuclei. We applied it to estimate the element abundance in r-process nucleosynthesis. We pointed out the importance of the mass-asymmetric fission process. In the actinide region where the fission process takes place, the mass-asymmetric fission is dominant and the mass division is essentially determined by the shell correction in the potential energy surface.