ua nt - p h / 06 01 04 9 v 1 9 J an 2 00 6 Atomic reflection off conductor walls as a tool in cold atom traps

We explain why a system of cold 85 Rb atoms at temperatures of the order T ≈ 7.78 × 10 −5 K and below, but not too low to lie in the quantum reflection regime, should be automatically repelled from the surface of a conductor without the need of an evanescent field, as in a typical atom mirror, to counteract the van der Waals attraction. The repulsive potential arises naturally outside the conductor and is effective at distances from the conductor surface of about 400nm, intermediate between the van der Waals and the Casimir-Polder regions of variation. We propose that such a field-free reflection capability should be useful as a component in cold atom traps. It should be practically free of undesirable field fluctuations and would be operative at distances for which surface roughness, dissipative effects and other finite conductivity effects should be negligibly small.