Hyperfine splitting and isotope shift in the optical transition

The laser-induced resonance fluorescence in an atomic beam was used in order to measure the hyperfine splitting of the 4ƒ76s2 8S7/2 and 4ƒ76s6p 6P5/2 levels in 151,153,155 Eu isotopes. The hfs constants A and B of the unstable 155Eu were determined for the first time: Aexp(155,8S7/2) = -8.78(3) MHz, Aexp(155,6P5/2) = -261.68(11) MHz and Bexp(155, 6P5/2) = -941(1) MHz. With these data and after corrections for second-order hyperfine structure perturbations the nuclear moments of 155Eu were deduced: μ(155) = 1.520(2) n.m. and Qs(155) = 2.494(20) b. In addition new and more precise values of the hfs constants of the excited state for the stable 151,153Eu were obtained. They are as follows: Aexp(151, 6P5/2 = -591.92(9) MHz, Bexp(151, 6P5/2) = -354.58(97) MHz and Aexp(153, 6P5/2) = -263.19(8) MHz, Bexp(153, 6P5/2) = -922.07(79) MHz. The hyperfine anomalies 151Δ153 = 0.74(4)% and 153Δ155 = 0.27(34)% were extracted from the corrected hfs constants