Measurement of the Stark shift of the Cs hyperfine splitting in an atomic fountain

We have used an atomic fountain frequency standard to perform a new measurement of the frequency shift induced by a static electric field E on the clock transition of the cesium 6²S1/2 hyperfine splitting. The result in units of Hz/(V/m)² is δν₀=-2.271(4)×10^-10E². The accuracy of this measurement represents a tenfold improvement over previous values. This result is of importance for testing ab initio theoretical calculations of the cesium atomic structure as well as semiempirical models used in parity violation experiments. It will also allow a better evaluation of the frequency shift induced by the blackbody radiation in cesium frequency standards.