Alkali metal atoms and small alkali clusters are classic heliophobes and when
in contact with liquid helium they reside in a dimple on the surface. Here we
show that alkalis can be induced to submerge into liquid helium when a highly
polarizable co-solute, C60, is added to a helium nanodroplet. Evidence is
presented that shows that all sodium clusters, and probably single Na atoms,
enter the helium droplet in the presence of C60. Even clusters of cesium, an
extreme heliophobe, dissolve in liquid helium when C60 is added. The sole
exception is atomic Cs, which remains at the surface
