Absolute frequency and isotope shift measurements of mercury 1S0–3P1 transition

We report the measurement of the absolute frequencies of the 6s2 1S0−6s6p 3P1 transition (253.7 nm) and the relevant isotope shifts in five mercury isotopes  198Hg,  199Hg,  200Hg,  202Hg, and  204Hg. The Doppler-free saturated absorption measurements were performed in an atomic vapour cell at room temperature with a four-harmonic generated (FHG) continuous-wave (cw) laser digitally locked to the atomic transition. It was referenced with a femtosecond optical frequency comb synchronized to the frequency of local representation of the International Atomic Time to provide traceability to the SI second by the 330 km-long stabilized fibre optical link. The transition frequencies and isotope shi…