光频标的原子分子结构和精密光谱的相对论计算

Cold atom optical frequency standard has promoted precise measurement at a new level. Meantime, unique energy structures of ultracold molecules will provide rich opportunities for precision measurement beyond that which is possible with cold atoms. Aiming at the 10-18 uncertainty of the time frequency and focusing on the precise laser control and the highly accurate calculation of errors arising from perturbation in external field, we shall investigate the electronic structure and precise spectra of atoms, ions, and ultracold molecules by using multi-electronic ab-initio calculations with the relativistic effect, the electronic correlation and themass-shift correction of atomic nucleus incorporated at the same foot. Our goals are to improve the precision of polarizability, evaluate rigorously various high-order quantities that affect the uncertainity of optical frequency standards, and find the magic wavelength and the tune-our wavelength, which will provide solid data support for breakthrough of the present precision level of frequency standard of our country. Further, we shall explore the prospective application of specific-state manipulation, precision spectral, and energy-level optimization of ultrocold molecule in molecule optical clock. We have developed the finite-field calculations of the polarizabilities and the black-body radiation shift of Al+, In+, and Sr and also accomplished the fully relativistic calculation of the ground and excited states of IrO molecule, having a certain research basis. This proposal will further enhance the multi-electronic calculation level of structure and spectra of atoms and molecules in order to gain truly "experimental precision measurement and theoretical understanding in detail."

冷原子光频标将精密测量提高到了新的水平，超冷分子独一无二的能级结构也为精密测量提供更丰富的机会。本项目围绕时频测量不确定度达到10–18水平的具体科学目标，针对原子、分子和离子光频标的精确激光调控和外场扰动导致误差的高精度评估，开展重原子、离子和超冷分子结构和精密光谱的多电子相对论计算，完备地考虑相对论效应、电子关联效应和原子核质量偏移修正，提高极化率的计算精度，严格评估影响频率不确定度的各种高阶小量，寻找魔幻波长和Tune-out波长，为我国突破现有原子频标精度水平提供数据支持，并探索定态量子调控和超冷分子精确谱线在冷分子光频标中的前瞻性应用。我们已经发展了Al+、In+、Sr的极化率和黑体辐射频移的有限场计算方法，并实现了IrO分子基态和激发态的全相对论计算，具备了一定研究基础。本项目的实施将进一步提升我国原子分子多电子结构计算水平，真正做到“实验上精密测量，理论上细说明白”。

该项目围绕时频测量不确定度达到10–18水平的具体科学目标，针对原子、分子和离子光频标的精确激光调控和外场扰动导致误差的高精度评估，开展重原子、离子和超冷分子结构和精密光谱的多电子相对论计算，在重原子分子结构、精密光谱和时间频率精密测量取得了一系列处于国际前沿的重要研究成果，主要包括：.1.提出了p4组态的四个高电荷态离子光学跃迁，不仅具有能级简单和品质因子高的优点，频率不确定度预期优于10-19，而且在钟跃迁附近存在强光学跃迁，为高电荷态离子的冷却提供了方法，完成了用于10-19精度量级的原子钟的类铝高价离子的不确定性评估，建议的一些高价离子光钟的候选体系为相关实验团队的高价离子光钟工作开展提供了初始的依据。.2.对光频标的精确激光调控和外场扰动导致误差的进行了研究，给出了Cd+微波离子钟的背景黑体辐射频移高精度数据；提出了Ca原子光钟的冷却囚禁的新方法；研究了Ca+离子光钟相关的谱线同位素偏移的相对论效应和光钟相关的跃迁谱线中质量偏移的相对论效应；确定了Yb原子光钟在红色失谐区域的几个重要的魔波长。.3.发展原子能级和结构性质的相对论计算方法，完成了Cd原子偶极极化率的高精度计算和同位素偏移因子与能量本征值的关联性研究，讨论了相对论效应、电子关联效应和原子核质量偏移修正对能级和原子性质的精度修正，为相关物理量的精密测量实验提供理论比对数据。.截至2018年12月，课题共发表SCI论文16篇， Phys. Rev. 系列文章8篇。