Abstract
We have precisely measured the hyperfine intervals and isotope shift of D1 lines of atomic lithium 6,7Li in a collimated atomic beam. The spectroscopy laser, an external-cavity diode laser (ECDL) with wavelength 670.9 nm, which is locked to a Fabry-Perot cavity by Pound-Drever-Hall technique, scans the spectrums by changing the cavity length. The reference laser is locked to molecular iodine transition. The laser-induced fluorescence signal is detected by photomultiplier, and the beat frequency between spectroscopy laser and reference laser is recorded. The results of 6,7Li for 2S1/2 hyperfine interval are 228.198 (12) MHz and 803.495(8) MHz. For 2P1/2 hyperfine interval, they are 26.108(9) MHz and 91.873(5) MHz. The isotope shift is 10533.800(15) MHz. Our results resolve the discrepancies between former measurements, and are consistent with most theoretical calculations.