Properties of multiply-charged Actinide Ions from Measurements of Rydberg Ion Fine Structure Patterns*

Multiply-charged actinide ions play a central role in actinide chemistry, but as highly relativistic many-electron systems their properties are difficult to predict from first principles. Experimental checks on these calculations are very sparse. One promising approach to determine the ion properties that control their long-range interactions is to attach a single non-penetrating Rydberg electron and measure the details of its binding to the ion of interest. This can be accomplished using the Resonant Excitation Stark Ionization Spectroscopy (RESIS) technique. The results of studies of the Rn-like and Fr-like ions of Th and U will be discussed.