Adiabaticity in the lateral electron-momentum distribution after strong-field ionization

By solving the time-dependent Schrodinger equation for atoms in short laser pulses of different polarizations, it is shown that in strong-field ionization without rescattering, the lateral width of the electron-momentum distribution corresponds adiabatically to the instantaneous laser field on a sub-laser-cycle time scale, as expected in pure tunneling ionization. In contrast to the distributions along the polarization direction, the width is affected little by depletion or Coulomb effects.