Trapping of Rb Atoms by ac Electric Fields

We demonstrate trapping of an ultracold gas of neutral atoms in a macroscopic ac electric trap. Three-dimensional confinement is obtained by switching between two saddle-point configurations of the electric field. Stable trapping is observed in a narrow range of switching frequencies around 60 Hz. The dynamic confinement of the atoms is directly visualized at different phases of the ac switching cycle. We observe about 10⁵ Rb atoms in the 1 mm³ large and several microkelvins deep trap with a lifetime of approximately 5 s