Coulomb and Rescattering Effects in Above Threshold Ionization
We present a generalization of the S-matrix theory of above-threshold ionization (ATI), which includes both the Coulomb and rescattering effects. The Coulomb effects are responsible for a considerable increase of the ionization rates, while the rescattering effects give rise to the appearance of the second plateau of the ATI spectrum. Coulomb effects change the behavior of the rates at the first plateau, but they do not influence the qualitative behavior of the spectrum of the high-energy electrons in the second plateau. Our results are in excellent agreement with recent experiments. We show that the sidelobe positions correspond to the last rounded top before the cutoff of the ATI spectrum for the corresponding angle. Our model is simple, and can be easily generalized to different inert gases.