Applicability of the Kramers-Henneberger approximation in the theory of strong-field ionization

Abstract

The ionization of the one-dimensional model system with a short-range potential by a linearly polarized laser field is studied by direct numerical integration of the non-stationary Schrödinger equation. The results are interpreted in terms of both field-free atomic states and Kramers-Henneberger (KH) eigenstates. The dynamics of the system is analysed to determine which potential (atomic or KH) is physically more appropriate to describe the ionization process. The justification of the KH approach is also examined. A new limitation of the validity of the KH approximation is found to exist in the case of low laser frequencies.