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”。

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."