Abstract

The long-range van der Waals attraction between an atom (or molecule) and a surface, scaling in C₃z^-3, is an essential feature of numerous cavity QED processes. In the case of an excited atom lying close to a dispersive dielectric medium, it has been predicted [1] that the interaction can be magnified, relatively to the attraction by a perfectly reflecting surface, when part of the virtual emission of the atom is coupled to the absorption spectrum of the dielectric surface. Such a coupling has been predicted for a Cs atom (6D_3/2) in front of a sapphire surface [2]. Indeed, the rather well-known spectrum of sapphire shows that [ε(ω)-1]/ [ε(ω)+1] is resonant around 12.21 µm, while the 6D_3/2 level can decay to a 7P_1/2 level by a transition around 12.15µm. High resolution (FM) selective reflection (SR) spectroscopy appears quite convenient for the probing of such an effect : it typically probes the vapour one optical wavelength away from the surface, has been repeatedly demonstrated to be a sensitive tool of the surface van der Waals interaction [3], and it enables excitation of the short-lived 6D_3/2 level in the vicinity of the surface.

© 1998 IEEE