Multiple ionization of neon, argon and xenon in a high-intensity Ti:Sapphire laser field (λ = 800 nm) has been studied. Ion yield curves of xenon versus laser intensity have been obtained for the first six charges. Curves of charges 2+ to 6+ present obvious structures which can be attributed to the occurrence of non-sequential ionization processes. Also, comparison of the ion yields of the first three charges of Ar with previously obtained results inside a different laser field (Nd:Glass laser λ = 1053 nm, τ = 600 fs) indicates that non-sequential ionization is strongly wavelength dependent.

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Using stable, intense fs Ti:sapphire laser pulses, a distinct difference between the multiphoton ionization of O 2 and Xe, which have the same ionization potential, was observed. Considering electron rescattering and dissociative recombination, a new model for the dissociation of O 2 at low intensities is proposed which can explain this observation.

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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.