Structure and Electromagnetic Moments Of Exotic Nuclei

核物理学的前沿领域之一是对远离稳定谷的原子核结构的研究。在原子核中，单粒子轨道随中子数和质子数的变化而变化，并且对变形的存在非常敏感。在单粒子转移反应中可以探测到单粒子的特性。光离子转移反应将在库仑势垒附近和每核子约40兆电子伏特的光束能量下进行研究。研究将集中在N=50和N=82中子壳闭包附近的富中子核和对理解恒星核合成很重要的轻核。这些研究将在密歇根州立大学的国家超导回旋加速器实验室（NSCL）、阿贡国家实验室的阿贡串联直线加速器系统（ATLAS）和橡树岭国家实验室的霍利菲尔德放射性离子束设备（HRIBF）中使用稀有同位素的加速束进行。其中一个重点是在减少对理论模型参数依赖的情况下提取光谱强度。核结构物理学的另一个挑战是理解核波函数的微观描述和基于核内核子集体运动的模型之间的平衡。这种平衡作为激发能和角动量的函数而变化，并且在远离稳定谷的原子核中可能与观察到的接近稳定谷的原子核的行为大不相同。本提案第二部分的重点是通过测量激发态的磁矩来解决单粒子配置与潜在的球形或变形核心的相互作用。逆运动学中的库仑激励技术已经建立，并在放射性束流（肋骨）上进行了试验。然而，最近用比过去更重的原子核和更高能量束进行的高统计实验发现，在这些方法在新的RIB设施上试用之前，需要解决几个问题。半神奇Tin-126将在HRIBF研究。将在ATLAS设施建立的一个新的研究方案将首先集中于低海拔状态的钐-150和钆-152以及α转移反应的效力。拟议活动的结构旨在对研究生和本科生以及博士后助理的教育和培训产生尽可能大的影响。该项目还将通过纳入女性或来自其他代表性不足背景的早期职业科学家，从而有助于提高核科学工作人员的多样性。这些早期职业学者参与前沿研究将为他们在高等教育、基础研究和应用研究、国家实验室和工业领域的职业生涯做好准备。预期的核物理结果在天文学中也很重要，可以理解宇宙中观察到的元素的丰度；在凝聚态物理中，了解瞬态超细场的微观组成；为了核能和国家安全，了解裂变碎片的性质和反应。

One of the frontier areas of nuclear physics is the study of the structure of atomic nuclei far from the valley of stability. In atomic nuclei the single-particle orbitals are expected to change as a function of neutron and proton number, and in addition are very sensitive to the presence of deformation. Single-particle characteristics can be probed in single-particle transfer reactions. Light-ion transfer reactions will be studied with beam energies near the Coulomb barrier and about 40-MeV per nucleon. Studies will concentrate on neutron-rich nuclei near the N=50 and N=82 neutron shell closures and light nuclei important to understand nucleosynthesis in stars. These studies will be carried out with accelerated beams of rare isotopes at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University, the Argonne Tandem Linac Accelerator System (ATLAS) at Argonne National Laboratory and the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory. One focus is to extract spectroscopic strengths with reduced dependence on theoretical model parameters. Another challenge in nuclear structure physics is to understand the balance between a microscopic description of the nuclear wave function and a model based on collective motions of the nucleons within the nucleus. This balance changes as a function of excitation energy and angular momentum and may be quite different in nuclei away from the valley of stability from the observed behavior of nuclei near stability. The focus of the second component of this proposal addresses, via measurements of the magnetic moments of excited states, the interplay of single-particle configurations with an underlying spherical or deformed core. The technique of Coulomb excitation in inverse kinematics is well established and has been tested on radioactive beams (RIBs). However, recent high statistics experiments carried out with heavier nuclei than in the past, and with higher energy beams, have uncovered several issues that need to be addressed before the methods are tried at the new RIB facilities. Semi-magic Tin-126 will be studied at HRIBF. A new program of research to be established at the ATLAS facility will focus initially on the low-lying states of Samarium-150 and Gadolinium-152 and on the efficacy of alpha transfer reactions. The structure of the proposed activities is designed to have as large an impact as possible on the education and training of graduate and undergraduate students, as well as postdoctoral associates. The project will also serve to enhance the diversity of the nuclear science workforce by including early career scientists who are women or come from other under-represented backgrounds. The participation of these early career scholars in the forefront research would prepare them for careers in higher education and basic and applied research, in national laboratories and industry. The anticipated nuclear physics results are also of importance in astronomy, to understand the abundance of elements observed in the cosmos; in condensed matter physics, to understand the microscopic components of the transient hyperfine field; and for nuclear energy and national security, to understand properties of and reactions on fission fragments.