摘要
锂离子精密光谱为束缚态量子电动力学的验证以及原子核结构的研究提供了独特的平台.本文综述了实验和理论联合研究团队近年来对6,7Li+离子3S1和3PJ态超精细劈裂的高精度理论计算与实验测量的研究成果.在理论方面,理论团队采用束缚态量子电动力学方法对3S1和3PJ态的超精细劈裂进行了计算,精确至mα6阶.在实验方面,实验团队分别通过饱和荧光光谱法和光学Ramsey方法对7Li+和6Li+离子的超精细劈裂进行了高精度测量,并由此提取了6,7Li核的Zemach半径.结果显示,6Li的Zemach半径与核模型计算值存在显著差异,揭示了 6Li核的奇异特性.这不仅为原子核结构的探索提供了重要信息,也将进一步推动少电子原子和分子的精密光谱研究.
Abstract
Precision spectroscopy of lithium ions offers a unique research platform for exploring bound state quantum electrodynamics and investigating the structure of atomic nuclei.This paper overviews our recent efforts dedicated to the precision theoretical calculations and experimental measurements of the hyperfine splittings of 6,7Li+ions in the 3 S1 and 3PJ states.In our theoretical research,we utilize bound state quantum electrodynamics to calculate the hyperfine splitting of the 3S1 and 3PJ states with remarkable precision,achieving an accuracy on the order of mα6.Using Hylleraas basis sets,we first solve the non-relativistic Hamiltonian of the three-body system to derive high-precision energy and wave functions.Subsequently,we consider various orders of relativity and quantum electrodynamics corrections by using the perturbation method,with accuracy of the calculated hyperfine splitting reaching tens of kHz.In our experimental efforts,we developed a low-energy metastable lithium-ion source that provides a stable and continuous ion beam in the 3S1 state.Using this ion beam,we utilize the saturated fluorescence spectroscopy to enhance the precision of hyperfine structure splittings of 7Li+in the 3S1 and 3PJ states to about 100 kHz.Furthermore,by utilizing the optical Ramsey method,we obtain the most precise values of the hyperfine splittings of 6Li+,with the smallest uncertainty of about 10 kHz.By combining theoretical calculations and experimental measurements,our team have derived the Zemach radii of the 6,7Li nuclei,revealing a significant discrepancy between the Zemach radius of 6Li and the values predicted by the nuclear model.These findings elucidate the distinctive properties of the 6Li nucleus,promote further investigations of atomic nuclei,and advance the precise spectroscopy of few-electron atoms and molecules.
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