Spectroscopic study of the 4f⁷6s^{2 8}S^o_7/2 - 4f⁷ (⁸S^o)6s6p (¹P^o) ⁸P_9/2,_7/2,_5/2, transitions in neutral europium-151 and europium-153: absolute frequency and hyperfine structure.

We report on spectroscopic measurements on the transition in neutral europium-151 and europium-15313 at 459.4 nm. The center of gravity frequencies for the 151 and 153 isotopes for the 4f⁷6s^{2 8}S^o_7/2 - 4f⁷ (⁸S^o) 6s6p (¹P^o) ⁸P_9/2 transition were found to be 652,389,757.16(34) MHz and 652,386,593.2(5) MHz, respectively. The hyperfine coefficients for the 6??6??(1 ???) 8 ??9/2 state were found to be A(151) =16 -228.84(2) MHz, B(151)= 226.9(5) MHz and A(153) = -101.87(6) MHz, B(153)= 575.4(1.5)17 MHz, which all agree with previously published results except for A(153), which shows a small discrepancy. The isotope shift is found to be 3,163.8(6) MHz, which also has a discrepancy with previously published results. Center of gravity frequencies for the 4f⁷6s^{2 8}S^o_7/2 - 4f⁷ (⁸S^o) 6s6p (¹P^o) ⁸P_7/2, and 4f⁷6s^{2 8}S^o_7/2 - 4f⁷ (⁸S^o) 6s6p (¹P^o) ⁸P_5/2 transitions will also be reported.