Investigation of the 6s6p³P₂-6s7s³S₁ transition of ytterbium atoms with modulation-transfer spectroscopy.

This article focuses on the precise measurement of the 6s6p³P₂–6s7s³S₁ transition frequencies in neutral ytterbium (Yb) isotopes using modulation transfer spectroscopy (MTS) combined with an optical frequency comb. The absolute frequency of this transition in the dominant isotope ¹⁷⁴Yb is determined to be 389,260,605.8 ± 3.2 MHz, revealing a significant deviation of over 100 MHz from previous measurements, which is attributed to earlier experimental limitations such as unsteady laser locking. The study also reports isotope shifts relative to ¹⁷⁴Yb and calculates hyperfine structure constants for the ¹⁷¹Yb and ¹⁷³Yb isotopes, providing improved accuracy and consistency with recent theoretical and experimental data. These results offer a refined frequency reference at 770 nm valuable for ytterbium-based atomic physics experiments, including optical atomic clocks and cold atom research.