Vortex precession in Bose-Einstein condensates: Observations with filled and empty cores

We have observed and characterized the dynamics of singly quantized vortice s in dilute-gas Bose-Einstein condensates. Our condensates are produced in a superposition of two internal states of Rb-87, with one state supporting a vortex and the other filling the vortex core. Subsequently, the state fil ling the core can be partially or completely removed, reducing the radius o f the core by as much as a factor of 13, all the way down to its bare value of the healing length. The corresponding superfluid rotation rates, evalua ted at the core radius, vary by a factor of 150, but the precession frequen cy of the vortex core about the condensate axis changes by only a factor of 2.