Resonance and ac Stark effects in three-photon ionization of Cs

Abstract
We present a theoretical analysis of an experiment on near-resonant three-photon ionization of Cs. We have calculated all parameters entering in the equations for the density matrix and have shown that previously invoked higher-order laser-induced Stark shifts are negligible. A complete solution of the equations suggests that the observed unusual dependence of the ion signal on laser intensity is the result of spatial beam effects.