We present a theory of spin polarization of electrons ejected from atoms by two-photon resonant three-photon ionization. Our treatment includes saturation effects and pays proper attention to the finite rise time of the laser pulse and the non-Lorentzian wings of the laser spectrum. Numerical results for the cesium atoms indicate that due to saturation effects the spin polarization is generally less than its value predicted by perturbation theory. The different saturation behavior of the ionization channels causes a saturation dip to develop in the degree of spin polarization.

• Received 8 August 1980

DOI:https://doi.org/10.1103/PhysRevA.24.318