Even-Parity Rydberg Series of Alkaline-Earth Elements

Even-Parity Rydberg Series of Alkaline-Earth Elements 

In this section we review isotope shift and hyperfine structure measurements concerning the even-parity Rydberg series msns and msnd 0 of Ca, Sr, and Ba, which have been studied most extensively up to now. Hyperfine interactions occurring in msns S Rydberg states can be readily understood and will be considered first. 

The finite electronic charge density at the nucleus gives rise to an electrostatic interaction with the nuclear charge distribution which represents a correction of the Coulomb potential of the nucleus experienced by electrons. In an optical transition a change 8p of the average relativistic total charge density across the nucleus may occur that manifests itself in the field shift contribution 

In this way the specific mass shifts and the changes in the mean square charge radii are eliminated. However, only relative changes in 

Figwe 20. Isotope shifts of even barium isotopes recorded for unperturbed (top row) and perturbed (bottom row) Ba Rydberg states. (Taken from Ref. 51.) 

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