Final State Interaction and Field Polarization Effects in the Multiphoton Ionization of Atoms
This paper deals with the role of the final state interactions in the multiphoton ionization of atoms by strong radiation fields. Considerable work has been devoted to this topic, and several aspects of it have been evidenced to various degrees along the years. The early papers neglected at all the interaction between the ejected electron and the residual ion1, and no systematic calculation was performed at orders higher than the lowest one; nevertheless, these early approaches qualitatively predicted most of the above-threshold-ionization phenomenology and only now it is becoming clear their actual potential and limits2, 3. Other approaches have tried to deal with the final state interactions suggesting that the experimental findings could be explained by means of electron scattering by the parent ion after the ionization4 or by ponderomotive scattering of the ejected electrons when leaving the laser beam5. This latter approach describes the ejected electron by a Volkov wave and let the electrons experience the time and space inhomogeneities of the laser beam, causing significant modifications of their energy and angular distributions. The experimental results appear qualitatively well reproduced by treatments relying on these mechanisms, which thus should be seriously considered for inclusion in a comprehensive, rigorous theory.
KeywordsStrong Field Atomic Spectrum Multiphoton Ionization Final State Interaction Weak Field Limit
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- 7.(a)F. Trombetta, S. Basile and G. Ferrante, “Nonperturbative Treatments of Nonresonant Multiphoton Ionization of the Hydrogen Atom. The Weak Field Limit”, J. Opt. Soc. Am. B (in press).Google Scholar