近库仑势垒能区^(7)Li+^(207)Pb体系光学势的阈异常现象  

Threshold Anomaly Phenomenon of Optical Model Potentials for ^(7)Li+^(207)Pb System at Energies Near Coulomb Barrier

作　　者：黄志杰 林承键[1,2] 杨磊 贾会明[1] 马南茹[1] 温培威[1] 杨峰 王丹英[1] 骆天鹏 常昶 段海锐 祝颂娴 尹诚 杨炅和 王浩睿 范泽睿 傅凌逸 李慧艳 HUANG Zhijie;LIN Chengjian;YANG Lei;JIA Huiming;MA Nanru;WEN Peiwei;YANG Feng;WANG Danying;LUO Tianpeng;CHANG Chang;DUAN Hairui;ZHU Songxian;YIN Cheng;YANG Jionghe;WANG Haorui;FAN Zerui;FU Lingyi;LI Huiyan(China Institute of Atomic Energy,Beijing 102413,China;College of Physics and Technology,Guangxi Key Laboratory of Nuclear Physics and Technology,Guangxi Normal University,Guilin 541004,China)

机构地区：[1]中国原子能科学研究院,北京102413 [2]广西师范大学物理科学与技术学院,广西核物理与核技术重点实验室,广西桂林541004

出　　处：《原子能科学技术》2024年第11期2255-2261,共7页Atomic Energy Science and Technology

基　　金：国家重点研发计划(2022YFA1602302);国家自然科学基金(U2167204,12175313,12235020,12275360);稳定支持基础科研计划;中核集团领先创新计划(LC202309000201)。

摘　　要：对于紧束缚核反应体系,光学势在近库仑势垒能区呈阈异常的现象。对于弱束缚核(如^(6)Li、9Be和6He)参与的反应,光学势呈反常的阈异常现象。然而,对于弱束缚核^(7)Li参与的反应,光学势行为仍存在争议。为此,本工作在近垒和深垒能区高精度测量了^(7)Li+^(207)Pb体系的弹性散射角分布,采用光学模型拟合并抽取了势参数,结果显示出阈异常的现象。此外,由深垒能区的数据确定了^(7)Li+^(207)Pb体系的反应阈值,约0.82VB(库仑势垒高度),介于典型紧束缚核16O+208Pb体系的0.93VB和弱束缚核^(6)Li+232Th体系的0.73VB之间。这意味着反应阈和破裂阈之间可能存在着关联,值得进一步研究。The nuclear interaction serves as a fundamental component in the investigation of the mechanisms underlying nuclear reactions.The optical model potential(OMP)is extensively employed to phenomenologically describe the interaction of nuclear collisions.It is well established that the OMPs are closely linked to the internal structures of the nuclei involved in the collision.Consequently,it follows that OMPs for weakly-bound systems will differ significantly from those of tightly-bound systems,a fact that has generated considerable interest in current research.For tightly bound nuclear systems,OMPs exhibit a threshold anomaly(TA)phenomenon in the energy region near the Coulomb barrier,where the connection between the real and imaginary potentials is well described by the dispersion relation.For weakly bound nuclei(such as ^(6)Li and 9Be)induced reactions,OMPs show an abnormal“threshold anomaly”phenomenon,where the connection between the real and imaginary potentials is well described by the dispersion relation.However,the behavior of OMPs remains controversial for the weakly bound nucleus ^(7)Li induced reactions.Therefore,this study is focused on the ^(7)Li+^(207)Pb system,aiming to measure and analyze its phenomenological OMP with precision.The experiment was carried out on the R60 nuclear reaction terminal of the HI-13 tandem accelerator located at the China Institute of Atomic Energy.In the present work,elastic scattering angular distributions of the ^(7)Li+^(207)Pb system have been measured with high precision at energies near and well below the Coulomb barrier.Through fitting the angle distributions of elastic scattering by the optical model,the OMP parameters of the ^(7)Li system were successfully determined.Although ^(7)Li was commonly considered as a weakly bound nucleus with a low breakup threshold,its OMP exhibits the typical threshold anomaly phenomenon:The real potential presents a bell-like shape around the barrier,and the imaginary potential decreases below the barrier and then falls quickly down t

关 键 词：光学势 弹性散射角分布 弱束缚核 阈异常 色散关系 

分 类 号：TL11[核科学技术—核能科学] O561[理学—原子与分子物理]