Resonant structures in the low-energy electron continuum for single ionization of atoms in the tunnelling regime

Abstract

We present results of high-resolution experiments on single ionization of He,\nNe and Ar by ultra-short (25 fs, 6 fs) 795 nm laser pulses at intensities\n0.15-2.0x10^15 W/cm^2. We show that the ATI-like pattern can survive deep in\nthe tunneling regime and that the atomic structure plays an important role in\nthe formation of the low-energy photoelectron spectra even at high intensities.\nThe absence of ponderomotive shifts, the splitting of the peaks and their\ndegeneration for few-cycle pulses indicate that the observed structures\noriginate from a resonant process.\n