Origin of the double-peak structure in the momentum distribution of ionization of hydrogen atoms driven by strong laser fields

Momentum distributions of electrons emitted from the H(1s) atom by linearly polarized, strong low-frequency laser pulses are studied. The origin of the double-peak structure observed in the distribution of the momentum parallel to the laser field polarization axis is investigated using a quasiclassical trajectory method including tunneling. We show that the double peak originates from the influence of the Coulomb force on the outgoing trajectories rather than from rescattering. Quasiclassical and quantum results agree qualitatively while differences resulting from interference effects are observed.