Cooling Neutral Atoms in a Magnetic Trap for Precision Spectroscopy

A configuration of magnetic fields is exhibited which can harmonically trap paramagnetic particles in a shallow field minimum, superposed on a nearly uniform field which simplifies spectroscopic interactions with the particles. The potential energy of a trapped neutral particle depends on the particle's internal quantum number, as well as its position in the trap, permitting a combined rf-laser optical pumping cycle which can cool particles by a factor of 2 per cycle. Application of these ideas to the trapping of Na atoms is discussed.