冷镱原子光钟绝对频率测量及相关跃迁研究的进展

At present, the stability and uncertainty of optical atomic clocks have reached the level of 10^-18, making them the most precise time-frequency measurement tools. Optical atomic clocks demonstrate potential for advanced scientific research in precision measurements and fundamental physics, potentially redefining the unit of time “second". Among optical clocks, ytterbium (Yb) atomic clocks stand out due to their unique energy level advantages, making them one of the most mature and extensively researched optical clock candidates worldwide. The absolute frequency measurement of the ytterbium atomic clock transition and the precise measurement of the ytterbium atomic correlation transition spectrum are essential. This article provides an overview of the domestic and international progress in absolute frequency measurement of 6s²¹S₀-6s6p ³P₀ clock transition of cold ytterbium atomic clocks. The experiment measures the absolute frequency of Ytterbium atomic clock transition with an uncertainty of 7.3×10^-16 is introduced whose measured value is 518 295 836 590 863.30±0.38 Hz. Additionally, we present the results of precision absolute frequency measurements of relevant repumping transitions at 649, 770, and 1 389 nm, which use the absolute-frequency-measured ytterbium atomic clocks as a reference.