Dielectric properties of a thin film consisting of a few layers of molecules or particles

An accurate model far the dielectric properties of a thin film consisting o f a few layers of particles (or molecules) is described. The depth dependen ce and the anisotropic behavior of the local permittivity due to the surfac e environment are studied. The method is described in terms of a general mu ltipole expansion, but the detailed derivation is carried out mainly in the framework of dipole approximation for the field interactions of particles. Both the static and harmonic cases are considered. Numerical results are p resented.