Electron Correlation Effects in Nonresonant Multiphoton Ionization Processes

The role of electron correlations in nonresonant multiphoton processes of atoms is presented. The evidence for the validity of a lowest order perturbation theory (LOPT) approach for the laser field in the case of nonresonant processes is sketched. The growing consensus for a LOPT interpretation of even the multiply-charged ion spectra obtained with high intensity lasers is reviewed. Finally, a review of those specific electron correlation processes within LOPT that are important for the quantitative prediction of two-photon ionization cross sections is presented and some of their effects on calculated generalized cross sections are exhibited