利用不稳定原子核的衰变研究核物质对称能的性质  

Properties of the nuclear symmetry energy studied by theradioactivity of unstable nuclei

作　　者：万牛[1] 许昌[1] Niu Wan;Chang Xu(School of Physics,Nanjing University,Nanjing 210093,China)

机构地区：[1]南京大学物理学院,南京210093

出　　处：《科学通报》2020年第7期594-609,共16页Chinese Science Bulletin

基　　金：国家自然科学基金(11822503,11575082,11535004,11375086)、国际科技创新合作重点专项(2016YFE0129300);中央高校基本科研业务费专项(南京大学)资助。

摘　　要：对称能可表征核物质中质子和中子的同位旋不对称效应,在核物理和天体物理方面都具有非常重要的作用,例如会对原子核的质量、奇特原子核的结构与性质、重离子核反应的物理机制、中子星的结构与成分和冷却过程等产生重要影响.目前人们对核物质对称能关于密度的依赖行为了解得还不够清楚,尤其是在高于饱和密度区域,对称能的性质还存在很大的不确定性.研究表明,除了二阶对称能,四阶对称能也会对中子星的冷却过程产生重要影响,也会影响到中子星壳的内侧边缘的具体位置等,进而影响到中子星的结构性质.利用Hugenholz-van Hove(HVH)基本定理,对称能的性质可以直接与核子单粒子势联系起来.不稳定原子核的衰变可以用于提取核子单粒子势的相关性质,也可以用于研究核物质对称能的密度依赖行为.In this paper,the properties of the symmetry energy in asymmetric nuclear matter,including the quadratic and quartic symmetry energies as well as their density slopes at the saturation density,are studied by the radioactivity of unstable nuclei.The symmetry energy was initially introduced as a quantum correction energy in the Weizsacker-Bethe liquid-drop model,which was proposed to describe the binding energies of finite nuclei.In order to systematically study the properties of the symmetry energy,the concept of the nuclear matter was introduced,which consists of neutrons and protons with finite neutron and proton densities but infinite neutron and proton numbers.By comparing the properties of the isospin symmetric nuclear matter,in which the neutron density is equal to the proton density,and those of the isospin asymmetric nuclear matter,in which the two densities are unequal,the symmetry energy is found to approximately represent the difference of the energy per nucleon in them.That is to say,the symmetry energy is an evaluation of the energy cost to convert protons in symmetric nuclear matter to neutrons in asymmetric nuclear matter.Since the symmetry energy characterizes the isospin asymmetric effect in nuclear matter,it plays critical roles in not only nuclear physics but also astrophysics.For example,the symmetry energy is closely related to the nuclear masses,the structures and properties of nuclei far away from stability line and near drip lines,the mechanism of heavy-ion reactions,the structures and component of neutron stars,the masses and radii of neutron stars,the cooling process of neutron stars,and so on.Besides of the quadratic symmetry energy,the quartic symmetry energy can have obvious effects on the properties of neutron stars as well.The quartic symmetry energy can significantly affect both the proton fraction inβ-stable neutron stars and the critical density for the direct Urca process,which leads to faster cooling of neutron stars.In addition,the quartic symmetry energy is found to be very i

关 键 词：对称能 原子核衰变 双折叠模型 结合能 液滴模型 

分 类 号：O571[理学—粒子物理与原子核物理]