Efficient 1-D Velocity Selection in Laser-Cooled Atom Clouds

Abstract

In this paper we demonstrate a “velocity-selection” technique which selects the lowest energy atoms from a laser-cooled cloud. The technique selects in one dimension, and confines the colder, selected atoms in a small auxiliary trap, spatially separated from hotter atoms. For one dimensional experiments, velocity selection can have an efficiency (defined as the fraction of the initial cloud which remains after selection) that varies as √U/kBT, where U defines a maximum energy and T is a cloud temperature, making it more efficient than 3D cooling methods such as evaporative cooling, which typically retains less than 1% of the atoms when cooling to 1% of the initial temperature [1]. The process of selection creates non-thermal distributions with a sharp cutoff in velocity, which can be important for experiments on effects such as tunneling [2] and quantum collisions [3].