Quantized vortices in a gaseous Bose-Einstein condensate.

Using a focused laser beam we stir a Bose-Einstein condensate confined in a magnetic trap. When the stirring frequency reaches a critical value, we observe the formation of a vortex at the center of the condensate. Using the quadrupolar excitation of the condensate we measure the angular momentum of the condensate with the vortex, and we find that it is ∼ ∼&hmacr; per particle, as expected. For larger stirring frequencies, regular arrays of vortices are observed. [ABSTRACT FROM AUTHOR]