Casimir-Polder interaction between an atom and a dielectric slab

We present an explicit analytic calculation of the energy-level shift of an atom in front of a nondispersive and nondissipative dielectric slab. We work with the fully quantized electromagnetic field, taking retardation into account. We give the shift as a two-dimensional integral and use asymptotic analysis to find expressions for it in various retarded and nonretarded limiting cases. The results can be used to estimate the energy shift of an atom close to layered microstructures.