核反应中动力学极化势的系统学研究

Optical model is the most successful phenomenological model describing direct nuclear reactions. The variation of imaginary optical model potential with respect to energy will produce the dynamical polarization potential in the real part, which is governed by the dispersion relationship. Many abnormal behaviors of the optical potential have been discovered during the 30 years study, such as the threshold abnormal, breakup threshold abnormal, diffuseness parameter abnormal, and inapplicable of dispersion relationship for halo nuclear system。New systematical study is in urgent need。Angular distributions of elastic scattering are mainly used to extract the dynamical polarization potential, which is often not unique and only the external region of the potential can be extracted. It’s proposed to combine the elastic scattering reaction, the transfer reaction and the fusing reaction so as to extract the dynamical polarization potential in this project. Firstly, the internal and external information of the optical potential can be completely extracted by combining different reactions. Secondly, by systematically analyzing the results that have been extracted, the scaling laws of potential parameters with respect to system size and energy can be obtained, as well as the general optical potential. These results will provide reference for the selection of potential parameters for the theoretical calculation in the absence of experimental data. Polarization potential in the optical potential is an overall representation of all dynamical effects during the reaction process. This application will study dynamical polarization potential from a new perspective and provide valuable clues for revealing deep-seated physical causes.

描述直接核反应的最佳宏观唯象模型是光学模型。由色散关系可以知道：变化的光学势虚势在实部产生一个动力学极化势，导致实势在库仑势垒附近产生一个剧烈的变化。近三十年的研究，人们发现了光学势阈异常、破裂阈异常、弥散参数异常、奇特核体系色散关系失效等新问题，急需要进一步的系统学研究。之前的研究主要采用弹性散射角分布抽取光学势，具有不确定性，并仅能抽取光学势外部信息。本申请提出结合弹性散射反应、转移反应和熔合反应，系统抽取动力学极化势。通过结合不同反应类型，可以完整的抽取光学势的内部和外部信息。系统学分析已经抽取的结果，可以得到势参数随体系和能量变化的系统学规律和普适的光学势，为缺少实验数据的情况下的理论计算提供势参数的选取依据。极化势是反应过程中所有动力学效应在光学势上的一个总体表象，本申请将从一个新的角度研究动力学极化势，为揭示深层次的物理原因提供有价值的线索。

近三十年的研究，人们发现光学势阈异常、破裂阈异常、弥散参数异常、奇特核体系色散关系失效等新问题，急需对重离子相互作用势开展进一步的系统学研究。本项目结合熔合反应、弹性散射反应和转移反应，通过多反应道系统抽取核核相互作用势的实部与虚部信息。首先，通过熔合反应，我们改进了传统耦合道模型，解决了原有模型中存在的数值不稳定问题；借助于该模型，发现Woods-Saxon相互作用势在描述深垒熔合抑制方面仍然可行，而不用引入新的相互作用势或者反应机制来解释该现象；通过采用Wong公式和SW熔合截面计算公式对大量实验熔合反应的系统学研究，我们得出了熔合势垒的新公式。其次，通过弹性散射和转移反应，我们首次成功把贝叶斯方法应用于光学势的研究中，研究了势参数先验分布对于后验分布的影响，发现后者对于前者非常敏感，采用不同的先验分布可以得出阈异常方面完全不同的结论。以上关于库仑势垒和光学势的研究成果，可以为实验上通过熔合反应或者多核子转移反应合成超重核，以及放射束流相关实验提供重要参考。