Enhanced nondipole momentum offsets in triple ionization of atoms driven by mid-infrared laser fields
We investigate the dependence on wavelength of nondipole effects in triple ionization of Ne driven by intense infrared and mid-infrared laser pulses using a three-dimensional semiclassical model that fully accounts for nondipole effects and the Coulomb singularity in the electron-core interaction. We find in triple ionization of strongly driven Ne a large positive average momentum offset along the direction of laser propagation, which vanishes in the dipole approximation. This positive momentum offset significantly increases with increasing wavelength of the laser pulse. This increase is present for all triple ionization events as well as for the main direct and delayed pathways of triple ionization. We attribute the increase of the momentum offset to the contribution of the effect of the magnetic field of the laser pulse on the bound electrons. This contribution counterbalances the decrease of electron-electron correlation in recollisions with increasing wavelength. We find that 1200 nm is an ideal wavelength for experimentally measuring the momentum offset related to correlated three-electron escape.