Neutral atomic beam cooling experiments at NBS

We have decelerated and cooled a neutral atomic sodium beam using a near resonant, counterpropagating laser beam. A spatially varying magnetic field compensates for the changing Doppler shift as the atoms decelerate, keeping the atoms in resonance with the laser. We have observed final velocities as low as 40 m/s, or about 25 times slower than the initial thermal velocity. By compressing the atomic velocity distribution we have increased the atomic density per unit velocity by as much as a factor of 30 over that of the thermal distribution.