Theory of Negative Ions in Liquid Helium

It is shown that Atkins' electrostriction model gives reasonable values for the mobility of positive ions in liquid helium. However, that model cannot account for the observed difference between positive- and negative-ion mobilities. Arguments are advanced in support of the "bubble" model; the negative ion is believed to be a free electron in a cavity of radius about 12 A. The bubble model leads to a mobility in fair agreement with experiment.