Multiphoton ionization saturation intensities and generalized cross sections from ATI spectra

Abstract
A simple method for the determination of saturation intensities and in some cases generalized cross sections in multiphoton ionization is presented. It utilizes the dependence of the ponderomotive shift on the laser intensity above the saturation limit. An application to He and Ar interacting with 500 fs pulses at 248 nm is demonstrated. Experimental results are compared with theoretical calculations.