Experimental Characterization of 1-D Velocity Selection
  We demonstrate a 1-D velocity selection technique which relies on combining magnetic and optical potentials. We have selected atom clouds with temperatures as low as 2.9% of the initial temperature, with an efficiency of 1%. The efficiency (percentage of atoms selected) of the technique can vary as slowly as the square root of the final temperature. In addition to selecting the coldest atoms from a cloud, this technique imparts a sharp cut-off in the velocity distribution. The cold selected atoms are confined in a small well, spatially separated from higher energy atoms. Such a non-thermal distribution may be useful for atom optics experiments, such as studies of atom tunneling. 
S. H. Myrskog, J. K. Fox, A. M. Jofre, L. R. Segal, S. R. Mishra, A.   M. Steinberg