We derive general expressions for the self-energy of a charged particle placed in the gap between two metal surfaces and near a metallic slab. Treating the electron gas in the metal within the hydrodynamic approximation, the self-energy of a charged particle is obtained, taking into account the dispersion of the surface plasmons and the effect of the recoil of the charged particle. We show that the self-energy saturates to a finite negative value at the metal surface and inclusion of recoil and dispersion reduces the magnitude of the self-energy.

• Received 7 July 1993

DOI:https://doi.org/10.1103/PhysRevB.48.15256