28Si中奇异圆环高自旋同质异能态实验寻找

The shape of the nucleus, as the basic nature of the nucleus, has long been one of the most interesting problems. It is also the physics quantity that can directly reflect the nuclear state and nucleon-nucleon interaction. As early as in the 1950s and 1960s, J. A. Wheeler predicted that the nucleus may assume a quasi-one-dimensional torus under certain conditions. The exist conditions and properties of the toroidal nuclei are studied in detail by following various microscopic theories. The applicant recently collaborated with Texas A&M University and found that there are 3 obvious resonance peaks in the high excitation energy region in 7 α decay channel of 28Si. The resonance peak located around 138MeV conforms to the energy of toroidal high spin state (THSI) with 44 hbar in 28Si, which is predicted by C. Y. Wong et al., and the subsequent toroidal shell model and the covariant density functional theory confirm these 3 peaks’ energies with THSI. It is shown that the energy, width, interval between peaks and the cross section of the 3 resonance peaks can be satisfactorily explained by THSI in the two theories. This application plans to make use of the 28Si beam of the Lanzhou heavy ion accelerator to confirm the exist of THSI in 28Si , with improving the angular resolution (energy resolution) for charged particles, adding the gamma detector, increasing event statistics, extracting the angular momentum range of these resonance peaks with antisymmetrized molecular dynamics model, and comparison the data with toroidal shell model and covariant density functional theory.

原子核的形状作为是原子核的基本性质一直是人们最感兴趣的问题之一，也最能直观反映原子核状态及核子相互作用的物理量，早在二十世纪五六十年代J. A. Wheeler预言在一定的条件下原子核可能呈现准一维的环形结构，随后各种微观理论对圆环核存在条件及性质进行了详细研究。申请人最近与德州农工大学合作，发现28Si 7α衰变道在高激发能区存在3个明显共振峰，138MeV共振峰与黄卓然等人预言的28Si中44 hbar圆环高自旋同质异能态（THSI）能量相符合，随后圆环壳模型（TSM）和协变密度泛函(CDFT)计算表明这3个共振峰能量、宽度、间隔及截面等都可以通过THSI得到满意的解释。本项目拟利用兰州重离子加速器28Si束流，提高带电粒子探测器角分辨（能量分辨）、增加γ探测器、增加统计，结合反对称化量子分子动力学提取共振峰角动量范围，与TSM和CDFT比较，确认THSI是否存在。

原子核的形状是人们最为关切的原子核的基本性质之一，它能够直接反映原子核状态和核子-核子之间的相互作用，通常情况下原子核处于球形附近或者具有椭球形变，早在二十世纪五六十年代J. A. Wheeler就预言原子核在在一定的极限条件下能够呈现准两维的环形结构，C. Y. Wong等利用各种微观理论方法对圆环核存在的条件及性质进行了详细的研究，但过去几十年实验上一直没有找到环形结构存在的证据。..本项目针对28Si中可能出现的高自旋、高激发能圆环结构进行研究，开展了实验方案的蒙特卡洛模拟，反应靶室，束流管道及探测器的研制；深入分析了15,25,35MeV/u入射能量下28Si束流打C,Si,Ta靶的实验数据。研究了28Si的各种类弹出射道产物，发现了大量的α共轭碎片发射，针对28Si的7种α共轭碎片出射道开展了仔细的分析，在7α道的激发能谱中发现在高能端有三个明显的共振峰。黄卓然等利用圆环壳模型(TSM)和孟杰等利用协变密度泛函理论(CDFT)的计算都和实验数据复合地比较好。这些共振峰能量远远高于目前已知分立共振峰所在能区，对人们对原子核高激发态及奇异形状的认识提出了严峻挑战。..在理论研究上，我们作为理论计算方与印度可变能量回旋加速器中心的B. Dey, D. Pandit等实验家合作，利用扩展的量子分子动力学模型(EQMD)模拟了16O+12C熔合产生28Si和20Ne+12C熔合产生32S复合核的动力学过程，发现在反应动力学过程中形成了由α团簇构成的奇异圆环构，α团簇可以在温度~2MeV和系统角动量~20 hbar的极端条件下存在 ，圆环结构的巨偶极共振能够描述28Si和32S热核的巨偶共振的奇异线形，解释了α共轭热核中雅克比形状转变消失的现象。