Abstract
The 2 2S1/2 ! 3 2S1/2 transition of atomic lithium has been measured by highprecision laser spectroscopy. A 735 nm Ti:Sapphire laser is used to excite the ground state atomic lithium from a weakly collimated atomic beam system. The excitation laser is stabilized by frequency lock to a specific comb line. The laser frequency is measured simultaneously by optical frequency comb with the accuracy to 10−12 level. The induced fluorescence spectrum of 2p-2s decay channel is fitted to the Voigt function to determine the transition line center. The SNR of the 6Li F=3/2-3/2 is up to 100. The center-of-gravity frequencies of 7Li and 6Li are 815618181.28(10) MHz and 815606730.20(6) MHz respectively. The hyperfine structure constants 93.30(10) MHz for 7Li and 35.40(10) MHz for 6Li are consistent with the previous data. However, the isotope shift is 11451.08(16) MHz and which disagrees with the previous measurements [8, 9, 11] and theorical calculation [7].