  In this paper we describe the rescattering process in optical field
ionization through a one-dimensional model, which improves the well-known
quasistatic model by adding the smoothed Coulomb potential in its second step.
The above-threshold ionization spectra and high-order harmonic generation are
calculated from this model. They are qualitatively in agreement with the
quantum results and experiments. In particular, we find that this model is
characterized by chaotic scattering. Modern nonlinear theory is used to analyze
this dynamical system. It is found that singular self-similar fractal structure
exists in the phase-dependence energy spectra, and the unstable manifolds
constitute the chaotic scattering pattern. Our results also demonstrate a close
connection of irregular trajectories with the energy spectra and high-order
harmonic generation. We conclude that the chaotic behavior plays an important
role in this one-dimensional model of optical field ionization.
