低丰度缺中子稳定原子核的起源及核反应截面研究进展  

The origin of low-abundance neutron-deficient stable isotopes and the relevant cross section measurements

作　　者：程浩 庞萱[2] 孙保华 Hao Cheng;Xuan Pang;Baohua Sun(China Institute of Atomic Energy,Beijing 102413,China;School of Physics,Beihang University,Beijing 102206,China)

机构地区：[1]中国原子能科学研究院,北京102413 [2]北京航空航天大学物理学院,北京102206

出　　处：《科学通报》2024年第21期3088-3098,共11页Chinese Science Bulletin

基　　金：国家自然科学基金(12325506,11922501)资助。

摘　　要：在质量数70~200范围内存在30多个低丰度、缺中子的稳定原子核(p-核).这些p-核的丰度(即它们占宇宙中总原子数的比例)很小,具体的合成机制尚不清楚,研究它们的起源是探索宇宙演化中不可或缺的一个重要环节.当前研究倾向于认为中重p-核主要通过γ-过程来合成,即在较高的恒星等离子体温度下,在已有种子原子核上发生光致裂解反应、继而衰变等过程而产生.γ过程涉及上千个低丰度原子核和不稳定原子核,由于光核反应截面低,实验数据稀少,相关的光核反应率主要依赖Hauser-Feshbach统计模型预言,核物理的不确定度因此成为制约解答p-核产生机制的难点之一.本文回顾了研究p-核的实验方法,总结了相关的研究进展,探讨了计划开展的研究工作.The synthesis of the elements beyond iron has been known to be dominated by the rapid neutron capture(r-process)and slow neutron capture(s-process).Nevertheless,approximately 30 stable,neuron-deficient isotopes between 74Se and 196Hg,known as the p-nuclei,cannot be synthesized in that way.This is because they are shielded by the valley ofβstability,which cannot be reached by the s-process and r-process flows.Theγprocess,also often referred to as the p-process,was proposed as one of the most promising candidates for producing the bulk of p-isotopes.The origin of these p-nuclei is explained by the burning of pre-existing more neutron-rich isotopes in stellar environments of high enough temperature(T9≡T/(109 K)=[2,3]),where photodisintegrations of such nuclei can occur.Such temperature conditions are fulfilled in the oxygen-/neon-rich layers of Type II supernovae(SNII)or in Type Ia supernovae(SNIa).Theγ-process starts with sequences of(γ,n)reactions.Several mass units away from stability,the(γ,n)reactions will compete with(γ,p)and(γ,α)reactions as well asβ-decays,leading to deflections in theγ-process path.Nowadays,the contribution of different stellar sources to the observed distribution of p-nuclei in the solar system is still under debate.The reliable modeling of theγ-process flows typically necessitates the consideration of an extensive network of approximately two thousand nuclei and thousands of reactions.The largest part of theγ-process reaction network lies in the region of neuron-deficient unstable nuclei,most of the reaction rates are not yet accessible by experiments.The scarcity of the relevant information makes it mandatory to rely heavily on rate predictions.Such predictions are exclusively based on the Hauser-Feshbach(HF)statistical model and the various nuclear ingredients required in such a framework.These nuclear ingredients include the optical model potential(OMP),gamma-ray strength function(GSF),and nuclear level density(NLD).It is important to test the reliability of these nuclear

关 键 词：原子核 元素起源 核合成 γ-过程 反应截面 

分 类 号：O571[理学—粒子物理与原子核物理]