These processes give the atom a small but not negligible speed and hence the gas has a temperature. If the slowest atoms could be made to neglect all the photons in the optical molasses, perhaps lower temperatures could be reached. But combining this method with laser cooling was difficult. Between 1988 and 1995 Cohen-Tannoudji and his group developed a method based on use of the Doppler effect, which converts the slowest atoms to a dark state. He and his colleagues showed that the method functions in one, two, and three dimensions.
Intensive development is in progress concerning laser cooling and the capture of neutral atoms.
Among other things, Chu has constructed an atomic fountain, in which laser-cooled atoms are sprayed up from a trap like jets of water. When the atoms turn at the top of their trajectory and start falling again, they are almost stationary. There they are exposed to microwave pulses that sense the atoms inner structure. With this technique it is believed that it will be possible to build atomic clocks with a hundredfold greater precision than at present.