Tunnelling coordinates of high-energy photoelectrons in above-threshold ionization

With a three-dimensional semiclassical ensemble simulation, we comprehensively analyse the underlying dynamics of the photoelectron energy plateau (with an energy ranging from 2U(p) to 10U(p), U-p is the ponderomotive energy) from the single ionization of atoms in strong linearly polarized laser fields. We study the initial tunnelling coordinates at the tunnel exit (tunnelling phase and initial transverse momentum) of those high-energy photoelectrons. The rescattering process is very sensitive to the initial transverse momentum at the tunnel exit. We further identify the significant role of the long-range Coulomb potential on the rescattering process, which is usually ignored for those high-energy plateau electrons. Depending on the initial tunnelling coordinates, multiple forward scattering plus a hard collision has a significant contribution to the yield of the high-energy photoelectrons. By analysing the tunnelling coordinates of rescattering electrons, this provides sophisticated information for other related rescattering processes, i.e., high-harmonic generation and nonsequential double ionization.