ua nt - p h / 06 01 03 1 v 1 5 J an 2 00 6 Dependences of the Casimir - Polder interaction between an atom and a cavity wall on atomic and material properties

The Casimir-Polder and van der Waals interactions between an atom and a flat cavity wall are investigated under the influence of real conditions including the dynamic polarizability of the atom, actual conductivity of the wall material and nonzero temperature of the wall. The cases of different atoms near metal and dielectric walls are considered. It is shown that to obtain accurate results for the atom-wall interaction at short separations, one should use the complete tabulated optical data for the complex refractive index of the wall material and the accurate dynamic polarizability of an atom. At relatively large separations in the case of a metal wall, one may use the plasma model dielectric function to describe the dielectric properties of wall material. The obtained results are important for the theoretical interpretation of experiments on quantum reflection and Bose-Einstein condensation. Recently the study of dispersion interactions between an atom and a wall has assumed a new significance in connection with Bose-Einstein condensates of ultracold atoms [1–3]. The van der Waals and Casimir-Polder forces acting between dilute individual atoms, confined in a magnetic trap, and a wall may influence the stability of a condensate and the effective size of the trap [3]. As was shown in Ref. [4], the study of the collective oscillations of the Bose-Einstein condensate can provide a sensitive test of dispersion forces. This prediction was later supported both theoretically [5] and experimentally [6]. Dispersion interaction between an atom and a wall is also taken into account in quantum reflection of cold atoms on a surface [7] and in dynamical interaction effects of fast atoms and molecules with solid surfaces [8]. Currently the new asymptotic behavior of the surface-atom interaction out of thermal equilibrium has been advanced [9]. Below we use the generic name " Casimir-Polder " for all atom-wall interactions of dispersion