Demonstration of a microwave trap for cesium atoms

We have trapped cesium atoms in the microwave field of a spherical resonator tuned to the blue of the ground state hyperfine splitting (∼9 GHz). Using 50 W of microwave power, the trap is quite shallow (10-100 μK) and large (radius ∼ 1 cm) and cannot hold cesium atoms up against gravity. We levitate atoms in the trapping state (F = 4, mF = 4 ground state) with a static magnetic field gradient. The trap is loaded with atoms cooled to 5 μK in an optical molasses. After a time the microwaves and gradient field are turned off and the trapped atoms are dropped and detected by a time-of-flight method. This experiment demonstrates the trap proposed for use with the strong-field seeking states of spin polarized hydrogen. Such states cannot be trapped using a static magnetic field