Three-dimensional relativistic calculation of strong-field photoionization by the phase-space-averaging method

Abstract

A relativistic treatment of strong-field photoionization based on the phase-space-averaging method is presented. A procedure is described for preparing a relativistic microcanonical ensemble of the atomic ground state and for calculating the final compensated energies for relativistic electrons. The method is applied to over-the-barrier ionization of hydrogen with ultrashort laser pulses. Ionization probabilities and electron energy spectra have been obtained for laser pulse amplitudes near and well above the atomic unit. The results are in excellent agreement with previous experiments under similar conditions. In sufficiently strong fields, saturation of ionization is shown to limit the attainable electron energies.