Laser intensity control over ionization asymmetry of hydrogen atom with a synthesized ω-2ω laser pulse

The ionization asymmetry of hydrogen atom in a synthesized 400–800-nm laser field is investigated by numerically solving the three-dimensional time-dependent Schrödinger equation. The left-right asymmetry of the threshold peak exhibits multiple reversals with the increasing 800-nm laser intensity. The photoelectron momentum distributions showthat the addition of 800-nm field leads to increasingly complex interference structures. By analyzing the partial-wave-resolved photoelectron energy spectra and coherent odd–even partial-wave pair contributions, we show that the repeated asymmetry reversals originate from the intensity-dependent redistribution of the contributing partial-wave components and the resulting changes in odd–even partial-wave interference. The accompanying redistribution of the projected excited-state populations is consistent with intensity-dependent changes in the effective multiphoton resonance conditions. The combined population and continuum analyses support a qualitative picture in which varying the 800-nm intensity redistributes the relative contributions of excitation and ionization pathways, thereby reshaping the outgoing partial-wave composition. This partial-wave interference picture provides important insight into multiphoton ionization dynamics and offers a route for coherent control of photoionization asymmetry in atomic and molecular systems.