EXPERIMENTAL REALIZATION OF A GRAVITATION AL CAVITY FOR NEUTRAL ATOMS

A parabolic electromagnetic reflector for slow cesium atoms is studied experimentally. This atomic mirror consists of an evanescent wave on a curved glass surface. A cloud of cesium atoms, trapped and laser coo led in a magneto-optical trap, is released a few millimeters above the surface, falls onto the reflector and is subsequently detected by flu orescence. It was observed to rebound more than 8 times. The mirror si ze and the reflectivity were studied, and reasonable agreement with a simple theory obtained. With 800 mW of laser power and a mirror of 1 m m diameter, we observed up to 73% of the atoms returning after each bo unce, the losses being mostly during the free flight between bounces.