Channel-closing-induced resonances in the above-threshold ionization plateau - art. no. 021401

Multiphoton resonances with ponderomotively upshifted Rydberg states are be lieved to have dramatic effects on the plateau of high-order above-threshol d ionization. For short pulses and intense laser fields, individual Rydberg states lose their physical significance. Under these conditions, on the ba sis of experimental and theoretical investigation of the dependence of the photoelectron spectra on the laser intensity, we propose that the observed effects can be largely understood in terms of the channel closings that are characteristic of a short-range model potential.