J-dependence of the isotope shift in Gd I 4f ⁷5d6s ²(a ⁹ D)

Abstract

The J-dependence of the isotope shift (IS) in the term a⁹D of 4f⁷5d6s² between six stable Gd isotopes was determined to be: z_5d(160−158)=20(2)MHz, z_5d(160−157)=34(4)MHz, z_5d(160−156)=40(4)MHz, z_5d(160−155)=50(5)MHz, z_5d(160−154)=73(6)MHz. The normalization with the corresponding δ〈r²〉 gives values z_5d/δ 〈r²〉 which are almost constant (mean value$\overline {z_{5d} /\delta< r^2 > }$=155(30)MHz/fm²). This indicates a CSO-effect of the spin-orbit interaction and the field shift operator.