共线激光光谱研究加速器离子的超精细结构和同位素位移

近年来随着加速器和激光技术的长足进步，原子物理高分辨激光光谱方法被成功应用于加速器离子束的实验研究工作，并以其信噪比高、分辨率好、可在线测量等巨大优势，逐步发展成为研究放射性核素原子核结构的首选方案，并被国际上几乎所有的著名加速器实验室采用。利用共线激光光谱方法精确测量原子基态能级的超精细分裂和同位素位移，我们可以得到高精度的并且与模型无关的原子核基本性质参数，拓展对弱束缚体系核素结构和核子有效相互作用势的认识。我们计划依托兰州重离子加速器（HIRFL），建设并完善国内首台面向加速器离子束的共线激光光谱仪，开展高精度共线激光光谱实验，获得同位素链原子完整的超精细结构跃迁谱线和同位素位移，分析原子核基本性质参数，验证实验方案可行性和实验装置的性能，为将来研究短寿命放射性核素打好基础。

With the development of accelerator and laser technology during the last 40 years, laser spectroscopy of atomic physics was successfully introduced into the studies of nuclear physics, and became one of the most important experimental methods to study the nuclear structure. Experimentally the laser spectroscopy measures the atomic levels of atoms and ions at the ppm level, determines the hyperfine structure and isotope shift of the atom in the ground and isomeric state, yields the model-independent nuclear structure information, including isotopic and isomeric nuclear spin, magnetic dipole moment, electronic quadrupole moment, and change in mean square charge radii. These nuclear fundamental parameters give important information about the competition and balance between nuclear shell and collective effects on the nuclear structure, and are used to describe the effective interaction between nucleons within nuclear system..There are several advantages that the laser spectroscopy becomes an unique and powerful tool to study the nuclear structure of radioactive beams at an accelerator. First, the key information on properties of nuclear ground state and isomers delivered from laser spectroscopy are the most exhaustive and accurate. Secondly, due to the large cross section of photon absorption and the high laser intensity within very narrow bandwidth, it is possible that the laser spectroscopy is sensitive enough to the rear isotopes from accelerator with very low production yield. Finally, the laser spectroscopy is generally performed after the isotope separator of the facility, so the isotopes studied have half-lives as low as a few tens milliseconds..Collinear laser spectroscopy is a special geometry designed high-precision laser spectroscopy, in which the atoms or ions are transported overlapping with laser beam collinear or anti-collinear. Combing with cooled and bunched ion beam and high-sensitivity detection system, such as RIS(Resonance Ionization mass Spectroscopy), the collinear laser spectroscopy can be used to study the short-lived isotopes and the low-production-yield isotopes. During the last decade, almost famous accelerator labs in the world have built their collinear laser spectroscopy for the nuclear physics study..So far there is none collinear spectroscopy based on the rear isotopes from accelerator or reactor in China. We are planning to construct a collinear laser spectroscopy set-up at HIRFL (Heavy Ion Research Facility in Lanzhou). Several stable and radioactive nuclear species will be studied by a variety of optical technologies. This will be a fundamental work for the future studies on the neutron-rich short-lived radioactive isotopes. In short, the state-of-the-art collinear laser spectroscopy will provide an unparalleled opportunity to study the exotic and short-lived nuclear species to the limits of nuclear stability.