Hyperfine-structure studies of La-139 I by diode-laser-based Doppler-Free spectroscopy

Sub-Doppler spectra of La-139 I were measured for four transition lines by using saturation absorption spectroscopy. For an atomic excitation laser. w e used a single-mode tunable diode laser with a master-oscillator power-amp lifier configuration. A La-Ar hollow cathode discharge lamp was used to gen erate La atomic sources. From the obtained spectra. we determined the hyper fine structure of the upper levels and the hyperfine constants A and B of t he La-139 isotope. Additionally, when the polarization intermodulated excit ation method was adopted, we could observe a decrease of velocity-changing- collision effects in the 675.30 nm transition line of La. compared with the case of saturation absorption spectroscopy.