Ramsey type Sub-Recoil Cooling
  We experimentally study the motion of atoms interacting with a periodically pulsed near resonant standing wave. For discrete pulse frequencies we observe a comb-like momentum distribution. The peaks have widths of 0.3 recoil momenta and a spacing which is an integer multiple of the recoil momentum. The atomic population is trapped in ground states which periodically evolve to dark states each time the standing wave is switched on. 
Frank Sander, Thibaut Devolder, Tilman Esslinger, and Theodor W.   Hansch