Measurements of the Hyperfine Structure and ΔF=+2 Transitions in Eu I by High-Resolution Diode-Laser Spectroscopy

High-resolution atomic-beam laser spectroscopy in Eu I has been performed using a tunable diode laser. The hyperfine structure (hfs) and isotope shift of the 4 f 7 6 s 2 8 S 7/2 –4 f 7 6 s 6 p 10 P 9/2 transition at 686.45 nm have been measured. The hfs constants A and B of 151 Eu and 153 Eu have been determined for the upper state 4 f 7 6 s 6 p 10 P 9/2 , and the hyperfine anomaly has been derived. The Δ F =+2 transitions, normally forbidden, have been induced by applying a magnetic field of approximately 1 G. Their intensity dependences on the magnetic field strength and on the hfs splittings agreed with the first-order perturbation theory, which considers the mixing between the closely lying hfs levels in the ground state.