Structure of positive impurity ions in liquid helium

Experimental study by Glaberson and Johnson of impurity-ion mobility in liquid He4 shows a dependence on core-ion species, contrary to the prediction of the Atkins model. We modify this model to improve its self-consistency and to take account of the electronic properties of the core ion. For the case of an alkaline-earth impurity, we find a structure similar to the electron bubble, owing to the presence of a remaining valence electron on the singly charged positive ion. The alkali ion structure differs only slightly from the Atkins form. Trends in the predicted radii are in qualitative agreement with experiment.