Theory of polarization shifts in exotic atoms

The level shifts caused by the electromagnetic polarizability of the nucleus (N) and the orbiting particle (H) are investigated in detail. The static E1 polarizability strongly dominates in levels with l>or=4 and the shift is given. The polarizabilities of other multipoles are calculated with the help of sum rules. The polarization of the electron cloud is a small modification of electron screening. The quasistatic approximation for the particle in the atomic orbit is justified by deriving a number of exact expressions for averages of excitation energies and their spread. (12 refs).