High-density trapping of cesium atoms in a dark magneto-optical trap.

We have confined magneto-optically trapped cesium atoms to densities of nearly 1012 cm-3 by directing most of the population to a hyperfine level which does not interact with the trapping light. This compression represents almost an order of magnitude improvement on the best density we have been able to attain in a conventional magneto-optical trap. In previous work such improvements in density have only been reported for much lighter sodium. We discuss and demonstrate the difficulties in applying the technique to a heavy alkalimetal atom and the limits that are imposed on the best combination of density and temperature that can be produced. We present a simple model that accurately reproduces the density behavior, and justify its basic assumptions by Monte Carlo simulation