3-DIMENSIONAL RELATIVISTIC CALCULATION OF STRONG-FIELD PHOTOIONIZATION BY THE PHASE-SPACE-AVERAGING METHOD

A relativistic treatment of strong-field photoionization based on the phase-space-averaging method is presented. A procedure is described fo r preparing a relativistic microcanonical ensemble of the atomic groun d state and for calculating the final compensated energies for relativ istic 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 agr eement with previous experiments under similar conditions. In sufficie ntly strong fields, saturation of ionization is shown to limit the att ainable electron energies. [S1050-2947(98)07201-1].