Hyperfine-structure anomalies of stable ytterbium isotopes

Hyperfine-structure anomalies of the stable ytterbium isotopes Yb171 (I=12) and Yb173 (I=52) have been measured in the two lowest-lying P13 states of the Yb atom. For the (4f)146s6p P13 level Δ=-0.367(9)%, while for the (4f)135d(6s)2 P13 level Δ=+0.084(22)%. The former result is the first conclusive evidence that the Nilsson model can account for the distribution of nuclear magnetism in highly deformed nuclei. The second result, in conjunction with the first, can be used to establish the amount of unpaired s-electron spin density in a state explicitly lacking in unpaired s electrons. If we neglect other forms of configuration interaction, we calculate that the core-polarization magnetic field produced by the 5d electron at the nuclear site is -1.7×105 G. Byproducts of our work have been the lifetimes of the two excited electronic states. We find Δ(6s6p P13)=7.6(8)×10-7 sec and Δ(f-1ds2 P13)=1.7(2)×10-8 sec.