Atom-wall interactions [1] are a key feature of atom dynamics in thin gas cells. For instance, for room-temperature alkali atoms with a residence time on the order of a few µs and a micrometer-thick cell, atoms are spending a thousand more time adsorbed on the wall than in free flight between the walls. In optical transmission spectroscopy, for vapour cells short enough to make the atomic free path anisotropic, the transient build-up of the resonant interaction with light is responsible for a specific enhancement of the response of the slowest atoms (i.e., atoms moving quasi-parallel to the walls): this provides the principle of a novel method for Doppler-free spectroscopy, applicable to a variety of situations (velocity-dependent optical pumping, linear absorption, two-photon transition, etc.). In the linear response regime, the free-flight coherent dynamics of the atom-light resonant interaction naturally leads to Dicke narrowing of the lineshape [2], which has been observed in the optical domain with its periodical decay and revival of the sub-Doppler optical resonance [3]. Extensions of Dicke coherent narrowing to multiphoton (two-photon or Raman-type) resonances have been recently analysed [4].
For smaller cell thickness, one enters the novel domain of dielectric nanocavity QED, in which van der Waals atom-surface interactions deeply alter the atomic response. Nanometre-thin vapour cells allow one to monitor van der Waals interactions in the yet unexplored 40-150 nm range, via modifications of the optical resonance lineshape [5]. Still open problems are the possibility of long range resonant coupling between atomic electronic excitation, and either surface-polariton modes [6] or waveguide modes in dielectric thin cells. On the other hand, Raman transitions between ground sublevels, or dark resonances, should in the principle allow one to explore long range Casimir interactions.
1. D. Bloch and M. Ducloy, "Atom-wall interaction", in "Advances in Atomic, Molecular and Optical Physics" (B. Bederson and H. Walther eds, Academic Press, San Diego, 2005) 50, 91
2. R. H. Romer and R. H. Dicke, Phys. Rev. 99, 532 (1955)
3. G. Dutier et al, Europhys. Lett., 63, 35 (2003) ; D. Sarkisyan et al, Phys. Rev. A 69, 065802 (2004)
4. G. Dutier et al, Phys. Rev. A 72, 040501(R) (2005)
5. I. Hamdi et al, Laser Physics 15, 987 (2005); M. Fichet et al, submitted for publication
6. H. Failache et al, Phys. Rev. Lett. 83, 5467 (1999); 88, 243603 (2002)