IMPURITY DYNAMICS IN BOSON QUANTUM FILMS

We calculate the binding energy and dynamic properties of He-3 atoms i n films of He-4 absorbed to graphite and several alkali metal substrat es. Without adjustable parameters, we obtain excellent agreement with the experimental binding energies for the ground state of the He-3 imp urity. We then introduce a time-dependent variational wave function to calculate dynamic properties of the impurity. The motion of the impur ity atom parallel to the surface is characterized by an effective mass due to hydrodynamic backflow. We also obtain the spectrum of excitati on energies and the lifetime of the excited states. When both lifetime and backflow effects are included, the energy of the first excited st ate of the impurity and the effective mass of the ground state, agree well with experimental data.