基于原子超精细结构的放射性核素核结构研究

Based on the laser ablation collinear resonant ionization spectroscopy developed at 2018 and applying the radioactive ion beam RIBLL at HIRFL, the present proposal aims to study the spin, magnetic dipole moment, electric quadrupole moment, nuclear charge distribution of calcium isotopes by high-precision measurement of atomic hyperfine structure. This project is supported by the national key discipline “Particle and Nuclear Physics” at Lanzhou University and the nuclear physics department cooperatively built by Lanzhou University and the Institute of Modern Physics recently. Two stable isotopes (40Ca and 48Ca) are magic in both proton and neutron number in the calcium isotopic chain, and doubly magic features also possibly exist in short-lived calcium isotopes far from the β stability. Hence, the study of calcium isotopes will benefit the understanding of the evolution of nuclear properties, which is significantly important for the unified description of the atomic nucleus. The resonance cross-section of the atomic physics process involved in the experimental method used here is much higher than that of the nuclear physics process, resulting in the extremely low demand of radioactive ion beam intensity. The present method is also a powerful tool to extract nuclear information in a nuclear model independent way, providing an important benchmark for the test of nuclear properties. The present investigation will accumulate experience for the nuclear structure study of radioactive nuclei based on the atomic hyperfine-structure measurement in China.

依托兰州大学粒子物理与原子核物理国家重点学科以及兰州大学与中国科学院近代物理研究所新共建的核物理系，本项目将利用2018年提出的激光烧蚀与共线共振电离相结合的新技术，基于兰州重离子加速器上放射性束流线RIBLL并整合现有资源，通过Ca同位素超精细原子光谱的精确测量，开展该同位素的自旋、磁矩、电四极矩、核电荷分布研究。Ca同位素链有两个稳定的双幻核，且远离非稳定线的一些Ca同位素也可能存在双幻核特征，因此其研究对更深刻理解核结构的演化，实现原子核统一描述具有重要意义。此外，本项目实验方法所涉及的原子物理过程的共振截面远远高于核物理过程的截面，对待测放射性核素流强要求极低，不仅如此，该方法所给出的核数据没有核物理模型的依赖性，能对核特性研究提供独立于核物理方法之外的检验。本项目将填补我国相关研究空白，为我国系统地利用超精细原子光谱测量开展放射性核素核结构研究打前站，积累经验。

核结构的变化会导致核外电子结构的细微变化，依托兰州大学粒子物理与原子核物理国家重点学科以及兰州大学与中科院近物所共建的核物理系，项目提出有机融合激光技术、原子物理与原子核物理，研究激光烧蚀共线共振电离技术，通过对核外超精细原子光谱的精确测量，为放射性核素核结构的研究和检测提供一种全新的、基于原子物理的研究手段。基于项目支持，我们搭建了激光烧蚀共线共振测量装置，开展了相关测量工作，并在搭建的实验装置和测量数据的基础上，进行了技术转化，研制了激光核素测量仪，用于军事和民用核设施中气态流出物中长寿命放射性核素的在线监测分析。在完成项目设定研究内容的基础上，我们又基于泵浦探测手段研究了空气激光的产生机制和分子电离动力学；采用激光探测技术，研究了原子、核子等微观粒子的跃迁动力学，相关研究为基于超快激光探测技术开展模拟核裂变研究提供了技术与基础数据支撑。