PLATEAU IN ABOVE-THRESHOLD IONIZATION SPECTRA

We present photoelectron energy spectra for the rare gas atoms in stro ng 40 fs, 630 nm laser pulses. A new property in the above threshold i onization distribution is described, namely, a plateau. Numerical calc ulations using one- and three-dimensional models suggest that at least in part this is a one-electron effect. All rare gas atoms investigate d show similar behavior, indicating that the plateau in above threshol d ionization is a universal phenomenon. We discuss a simple mechanism possibly responsible for the plateau.