Isotope shifts of perturbed 6sns 1 S 0 and3 S 1 Rydberg states of odd barium isotopes

Isotope shifts of the pairs Ba 135–138 and 137–138 have been measured for the 6sns ¹ S ₀ (11≦n≦23) and 6sns ³ S ₁ (14≦n≦23) Rydberg states. A quantitative analysis of the data in terms of hyperfine-induced singlet-triplet mixing was carried out. Admixtures of local perturbers belonging to the 5d 7d configuration were easily identified and admixture coefficients were derived.