On the Use of the Kramers-Henneberger Hamiltonian in Multi-photon Ionization Calculations

Abstract

We employ the Kramers-Henneberger Hamiltonian for time-independent calculations of two-photon ionization of atoms with one and two electrons. As compared to the electromagnetic interaction in the length and velocity gauges, the presently employed Kramers-Henneberger gauge has an advantage of the dipole matrix elements for the free-free electron transitions being finite and well-defined quantities. This circumstance simplifies considerably the computations and allows us to obtain accurate results for the two-photon ionization of realistic atomic systems.