Coulomb effect in multiphoton ionization of rare-gas atoms

Using 200 fs, 800 nm Ti:sapphire laser pulses to ionize noble atom gases, the ion versus intensity curves of these gases were obtained. By comparing the experimental curves with those obtained using different theoretical ionization rates, it was found that the inclusion of the effects on the ionization rate of the long-range Coulomb potential of the parent ion through quasi-classical perturbation theory (as proposed by Perelomov et al and Krainov) gives a rather good overlap with the experimental results.