Laser cooling of cesium atoms in gray optical molasses down to 1.1 mu K

We have studied the behavior of cesium atoms cooled in six-beam ''gray'' optical molasses. Cooling occurs for a laser detuned to the blue side of the 6S(1/2),F=3-->6P(3/2),F'=2 transition, and a Sisyphus-type effect accumulates the atoms in states not coupled to the light. We measure a minimum temperature of 1.1+/-0.1 mu K at low atomic density. The typical cooling time is on the order of 1 ms. A linear dependence of the temperature versus atomic density is found with a slope of similar to 0.6 mu K/(10(10) atoms/cm(3)).