International Effort Develops New Atom Cooling Method for Space Clocks

In a collaborative theoretical effort, A.V. Taichenachev, A.M. Tumaikin and V.I. Yudin of Novosibirsk State University and Leo Hollberg of the National Institute of Standards and Technology (NIST) in Boulder have developed a concept for two-dimensional sideband Raman cooling and Zeeman state preparation in an optical lattice. The development of this concept was driven by the need to reduce transverse velocities of laser-cooled space clocks as well as for cesium-fountain clocks on Earth. The approach suggested in their recent paper appears to be both simpler and more effective than previously proposed methods and has two significant advantages: the method only requires laser beams transverse to that atomic fountain direction, and the cooling process simultaneously pumps atoms into the desired ground-state energy level. The theory predicts that 95% of the atoms can be cooled to transverse temperatures of about 100 nK. An experimental apparatus designed to test the effectiveness of this cooling method is now under development at NIST.