J-dependence in the isotope-shift of the 4f75d6s a10D-term in the ground-configuration of Gd II
In order to extend the parametric description of the isotope shift to 5d-electrons in the lanthanides the IS of three GdII transitions (4f75d6pz10F11/2→4f75d6sa10D9/2, 11/2, 13/2) was measured with enriched isotopes and natural composition of Gd in hollow cathodes. The values −99.75(30)mK, −100.15(25)mK and −101.90(50)mK were obtained for the IS (between156Gd and160Gd) from the lines 367.1 nm, 374.4 nm and 385.6 nm resp. From theJ-dependence of the IS found in the a10D multiplet the crossed-second-order parameterz5d=1.40 (35) mK was calculated. After normalization withδ〈r2〉 andζ5d the figurez5d, norm=6.2(1.8)· 10−6 fm−2 agrees fully with the corresponding value from Eu I. This proves that theJ-dependence within a multiplet arises mainly from a crossed-second-order effect, which is originating from the field shift operator and operators of magnetic interactions.