基于多核子转移反应的动力学形变与新核素产生机制研究

The production of neutron-rich heavy or superheavy nuclides in the multinucleon transfer reaction is a frontier topic in the basic research of nuclear physics. These nuclides are not only helpful to the study of the nuclear structure and decay properties under extreme conditions, but also essential to the understanding of the r-process and the formation of elements heavier than iron in the stellar evolution process. In the multinucleon transfer reaction with near barrier energy collision, due to the coupling of relative motion and collective motion, and the strong attraction of short-range nuclear force, the reaction partners are no longer in their corresponding static deformation states, and the reflection asymmetric pear shaped octupole deformation begins to play an important role. Nevertheless, the detailed dynamical deformation mechanism is still unclear, and the study of the octupole deformation effect is also rarely involved. In view of this, the project of this application will focus on the dynamical deformation effect, and establish a multidimensional potential energy surface including the reflection symmetric quadrupole deformation and the reflection asymmetric octupole deformation. By solving the master equation, the dynamical deformation mechanism and its effect on the fragment formation in the multinucleon transfer reaction will be studied. Our research is expected to clarify the evolution characteristics of the octupole deformation, reveal the dynamical process of multinucleon transfer reaction, and provide some suggestion for the laboratory to produce new neutron-rich nuclides of interest.

利用多核子转移反应产生丰中子重核或超重核是当前核物理基础研究的前沿课题。这些新核素的产生有助于极端条件下原子核结构及其衰变性质的研究，同时对快中子俘获过程及恒星演化中超铁元素产生机制的理解至关重要。在近垒碰撞的多核子转移反应过程中，由于相对运动与集体运动的耦合，以及短程核力的较强吸引，原子核的形状不再处于静态形变，反射非对称的、呈“梨形”构型的八极形变开始扮演重要角色。然而，目前动力学形变的具体机制尚不清楚，对八极形变的研究少有涉及。鉴于此，本申请项目以动力学形变为研究对象，建立包含反射对称的四极形变自由度和反射非对称的八极形变自由度的多维势能面，通过求解多变量的主方程，探究多核子转移反应的动力学形变机制及其对碎片产生过程的影响。本申请项目的研究有望阐明八级形变的演化特征，深入揭示多核子转移反应的动力学过程，为实验室产生感兴趣的丰中子新核素提供新的思路。

超重核合成、丰中子新核素产生机制研究是核物理领域的前沿问题之一。最新实验发现多核子转移反应在产生N=126附近的丰中子新核素方面优势显著。本项目在前期关于动力学形变的基础上，通过不同核区同位素弹核与锕系靶核的多核子转移反应，系统探讨了入射道效应，阐明了锕系弹靶系统对产生锕系丰中子重核方面的优势；进一步探究了包含反射非对称八极形变的形变空间对势能面的贡献；此外，尝试发展可以合理描述大形变问题的方法，Cassinian ovals parametrization，为统一框架下描述多核子转移反应和熔合反应的形变演化机制提供新思路。