基于HIRFL-RIBLL1装置开展的极丰质子核衰变研究进展  

Progress on decays of extremely proton-rich nuclei based on the HIRFL-RIBLL1 facility

作　　者：林承键[1,2] 徐新星 孙立杰[1] 贾会明[1] 杨磊[1] 马南茹[1] 王东玺[1] 杨峰[1] Chengjian Lin;Xinxing Xu;Lijie Sun;Huiming Jia;Lei Yang;Nanru Ma;Dongxi Wang;Feng Yang(Department of Nuclear Physics,China Institute of Atomic Energy,Beijing 102413,China;College of Physics and Technology,Guangxi Normal University,Guilin 541004,China)

机构地区：[1]中国原子能科学研究院核物理研究所,北京102413 [2]广西师范大学物理科学与技术学院,桂林541004

出　　处：《科学通报》2021年第27期3527-3536,共10页Chinese Science Bulletin

基　　金：国家重点研发计划(2018YFA0404404);国家自然科学基金(11635015,U1732145,11705285,U1867212,11805280,11961131012);财政部稳定支持科研项目(WDJC-2019-13);中核集团领创科研项目(LC192209000701,LC202309000201)资助。

摘　　要：远离β稳定线原子核的衰变是当前核物理领域的一个前沿热点.本文回顾了近年来在HIRFL-RIBLL1上开展的轻核区极丰质子核的衰变研究.首先介绍实验方法,包括β-p-γ符合测量的探测器阵列以及当前发展的连续束注入-衰变方法.随后重点介绍^(22)Si和^(27)S的衰变研究及相关话题,包括国际现状和国内工作的进展.在^(22)Si衰变研究中,发现了奇特的β2p衰变模式,由此首次从实验上确定了^(22)Si的质量.此外,与^(22)O的β衰变作对比,发现跃迁到子核第一个1^(+)激发态的不对称性达209%,是迄今为止最大的镜像不对称性,为探索同位旋破缺提供了新线索.在^(27)S衰变研究中,观察到28条衰变分支,其中24条βp分支是新发现的,由此构建了完善的衰变纲图.进一步,推导出了^(26)Si(p,γ)^(27)P热核反应率,探讨了在新星和X射线暴场景中对星际26Al核合成的影响.The decay of the nucleus far from theβ-stability line is a currently hot topic in the field of nuclear physics.Research progress on decays of extremely proton-rich nuclei in sd shell based on the HIRFL-RIBLL1 facility is reviewed in this paper.The detector array mainly consists of 3 double-sided silicon strip detectors for implanted heavy-ions as well as decayed protons,4 quadrant silicon detectors for emittedβ-particles,and 5 Clover-typeγ-ray detectors.With this setup,a continuous beam implantation-decay method was developed for theβ-p-γcoincident measurement.Thanks to the excellent performance of the detection system,high precisionβ-decay spectroscopies of 15 proton-rich nuclei in sd shell have been obtained.For two typical cases,^(22)Si and^(27)S,their decays as well as related topics are presented in detail.In the study of^(22)Si decay,the half-life was determined as(28.6±1.4)ms,where the influence ofβp decay of daughter nucleus21Mg was taken into account.An exoticβ2p decay mode was discovered for the first time by tracking two decayed protons.Consequently,the mass of^(22)Si was deduced by the Coulomb displacement energy of isobaric analogue state.The 2p separation energy is-108(125)ke V,indicating that^(22)Si is a very marginal candidate for 2p ground-state emission.This result is in good agreement with the mass predication by the chiral effective field theory with 3-nucleon forces.Together with 3 branches ofβp decay,the decay scheme of^(22)Si was established.Comparing with theβdecay of^(22)O,a hitherto largest mirror asymmetry up to 209%was found in transition to the first 1^(+)excited state of the daughter nucleus.Shell-model calculations with isospin-nonconserving forces reproduced the observed data,attributing the large mirror asymmetry to the s1/2proton-halo state of^(22)Al.It provides another means to identify halo nuclei and a new clue to explore the isospin breaking.In the study of^(27)S decay,the half-life was determined as(16.3±0.2)ms,which is the most precise one so far.A total of^(27)

关 键 词：极丰质子核 β延迟衰变 半衰期 衰变纲图 镜像不对称性 热核反应率 

分 类 号：O571.3[理学—粒子物理与原子核物理]