Diagnostic technique for Zeeman-compensated atomic beam slowing: Technique and results

We have developed a diagnostic tool for the study of Zeeman-compensated slowing of an alkali-metal atomic beam. Our time-of-flight technique measures the longitudinal velocity distribution of the slowed atoms with a resolution below the Doppler limit. Furthermore, it can map the position and velocity distribution of atoms in either ground hyperfine level inside the solenoid without any devices inside the solenoid. The technique reveals the optical pumping effects and shows in detail how the slowing within the solenoid proceeds. We find for Na that most atoms in the chosen hyperfine state are decelerated in the slowing process. The width of the velocity distribution is determined mainly by inhomogeneities in the slowing laser beam. Using the central most uniform part of an expanded laser beam, the width is reduced to 2.5 m/s, corresponding to 3.2 mK. Finally, we discuss and show a method to produce a beam with two-velocity components for the study of head-tail low-energy collisions.