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 approximate to 14 mW of rf power acting on atoms approximate to 100 mu 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.