DYNAMICS OF HE-3 IMPURITIES IN HE-4 FILMS

Using a microscopic variational theory we calculate the binding energy of He-3 impurities in films of He-4 absorbed to a graphite substrate. Without adjustable parameters, we obtain excellent agreement with the experimental binding energies for the ground state of the He-3 impuri ty. To calculate excited stoles, we then introduce a lime-dependent va riational wave function. In that way, the impurity acquires a hydrodyn amic effective mass for its motion parallel to the surface due to hydr odynamic backflow. Excited states have a finite lifetime. When these e ffects are included, both the energy of the first excited state of the impurity, and the effective mass of the ground state, also agree well with experimental data.