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

基于涨落耗散动力学，研究了超重质量区的聚变反应和锕系元素区的多模态裂变反应。用多维朗之万方程进行了数值计算。用四维朗之万方程研究了两个离子接触后超重核的形成。我们指出了颈部自由度在接触初期的重要性，因为它的惯性很小。我们研究了锕系原子核的多模态裂变。我们研究了核摩擦系数对碎片质量和动能分布的影响。我们指出，在推导核摩擦系数时，同时拟合几个物理量是很重要的。对于接近的相位，我们计算了考虑两个离子的变形和取向的捕获概率。我们指出，在深度非弹性碰撞中确定的原始表面摩擦强度可能需要重新检查以研究融合过程。我们研究了朗之万方程作为随机微分方程（SDE）的性质。在SDE积分中，随机积分有几种解释方法，如Ito积分和Stratonovich积分。我们比较了两种解释下核聚变和裂变过程的数值结果。我们还对富中子核的裂变势垒进行了系统的研究。我们用它来估计r过程核合成中的元素丰度。我们指出了质量不对称裂变过程的重要性。在发生裂变过程的锕系区，质量不对称裂变占主导地位，质量划分本质上是由势能面的壳修正决定的。

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.