Elastic and inelastic evanescent-wave mirrors for cold atoms

We report on experiments on an evanescent-wave mirror for cold Rb-87 atoms. Measurements of the bouncing fraction show the importance of the Van der W aals attraction to the surface. We have directly observed radiation pressur e parallel to the surface, exerted on the atoms by the evanescent-wave mirr or. We analyze the radiation pressure by imaging the motion of the atom clo ud after the bounce. The number of photon recoils ranges from 2 to 31. This is independent of laser power, inversely proportional to the detuning and proportional to the evanescent-wave decay length. By operating the mirror o n an open transition, we have also observed atoms that bounce inelastically due to a spontaneous Raman transition. The observed distributions consist of a dense peak at the minimum velocity and a long tail of faster atoms, sh owing that the transition is a stochastic process with a strong preference to occur near the turning point of the bounce. (C) 2001 Academie des scienc es/Editions scientifiques et medicales Elsevier SAS.