Hyperfine structure studies of neutral europium transitions at 601.815 and 580.027  nm by saturation absorption spectroscopy.

We report Doppler-free spectroscopy of neutral europium carried out using the saturation absorption technique. In the present experiment, Eu/Ne hollow cathode discharge is used as an atomic vapor source of europium. The Eu transition 4f ⁷ 6s ² (S8 _7/2° )→4f ⁷ 6s6p(P8 _9/2 ) at 601.815 nm and 4f ⁷ 5d6s(aD10 _13/2° )→4f ⁷ 5d6p(zD8 _11/2 ) at 580.027 nm are investigated. The frequency separation between the adjacent hyperfine transitions as well as hyperfine structure (HFS) constants are calculated from the obtained experimental spectra. The HFS constant obtained for the state 4f ⁷ 6s6p(P8 _9/2 ) are A ¹⁵¹ =664.8  MHz; B ¹⁵¹ =293.5  MHz, and for state 4f ⁷ 5d6p(zD8 _11/2 ), the values are A ¹⁵¹ =7.6  MHz; B ¹⁵¹ =-60  MHz. These obtained values are in good agreement with the results reported in the literature using laser induced atomic beam fluorescence technique.