We present a generalization of the Keldysh-Faisal-Reiss model that includes the second-order $S$-matrix element and thus the effects of rescattering. On the example of a screened Coulomb potential we show that using our model it is possible to reproduce all main features of the recent experimental results, mainly, the appearance of a plateau, the position of the cutoff, and the side lobes. We also show that the difference between the direct ionization probability and the rescattering plateau for a long-range Coulomb-like potential (with a small screening parameter) is very large, which is in discrepancy with the experimental results. This indicates that the effective potential that an electron feels during the rescattering is not a pure Coulomb potential. We show that this potential can be approximated by a screened Coulomb potential with a properly chosen screening parameter.

• Received 30 October 1997

DOI:https://doi.org/10.1103/PhysRevA.57.5002