The Stark effect of the hyperfine structure of cesium

We present an overview of the quadratic Stark effect in the ground state of alkali atoms. On the basis of symmetry arguments we show that the second order Stark interaction vanishes in the spherically symmetric S-1/2 ground state while an extension of the perturbation theory to third order, including the hyperfine interaction, leads to scalar and tensor polarizabilities. We discuss the effect on the hyperfine structure of the Cs ground alpha((3))(2) (F = 4), which are in very state. We report 2 new independent measurements of the tensor polarizability 2 good agreement with prior experiments, and we present an extension of the theory of the Stark interaction which bridges a 40 year old discrepancy between experimental and theoretical values of the tensor polarizability. We also report the presence of a sign error in prior theory and discuss its relevance for primary frequency standards.