We have observed interactions between collimated monoenergetic beams of charged vortex rings. The cross section for ring-ring interaction is approximately geometrical, consistent with a hydrodynamic interpretation. Capture of free ions by oppositely charged rings has also been observed.
Electrons carried by vortex rings toward a free surface in liquid He4 are found to evaporate from the surface with an energy independent of the ring energy. The energy of the electron is found to depend upon the amount of charge stored near the surface. We find also that the percentage of the ring current which crosses the surface depends on temperature, ring energy, and conditions at the surface. Finally, we hypothesize a trapped state near the surface and analyze our results in terms of the lifetime of this state.