Radio-frequency ac Zeeman force for ultracold atoms

We measure the ac Zeeman force acting on ultracold ^87Rb atoms due to a radio frequency (rf) field driving intramanifold Zeeman transitions near 8 MHz. We observe about 2. 5 times the force of gravity for 14 mW of rf power acting on atoms 1004pt{0ex}m from the atom chip. Our measurements are consistent with theoretical predictions and demonstrate the spin-state dependence of the force, as well as its resonant and bipolar behavior. We demonstrate the ac Stern-Gerlach effect by spatially separating a spin mixture, using initial detuning to determine which spins are ac Zeeman high- and low-field seekers. With an eye towards using this force for atom trapping, we observe the time dependence of dressed state spin mixing as a function of detuning and power.