A Coulomb-included model for high-order harmonic generation from atoms

In strong laser–atom interactions, the Coulomb potential can affect the trajectories of rescattering electrons in high-order harmonic generation (HHG). Here, by constructing a semi-analytical Coulomb-included model and comparing it with numerical experiments that allow extraction of electron-trajectory information, we identify the role of the Coulomb potential in different processes of HHG. We show that the symmetry of the system determined by the Coulomb potential plays an important role in the ionization process of HHG, inducing the tunneling-out time of electrons to shift toward earlier times. This symmetry-related effect reflects the quantum properties of atomic systems, in sharp contrast to the classical Coulomb-induced acceleration in the recombination process. In particular, compared with other strong-field models, the scaling law of the amplitude of HHG electron trajectories predicted by this model agrees with numerical experiments, indicating that the model developed here can be used to quantitatively describe HHG. This model can also be used to study strong-field ionization significantly influenced by rescattering.