Features of the energy spectra of photoelectrons at the atomic ionization in a two-color laser field of first and third harmonics

Classical analysis and quantum-mechanical studies of the energy spectra of photoelectrons have been carried out for above-threshold ionization of atoms in a two-color laser field of the first and third (n = 3) harmonics. Numerical computations show that the boundary of direct ionization plateau corresponds to the electron energy E ≈ 3.56 \(U_{p_1 } \), while the boundary of rescattering plateau corresponds to the electron energy E ≈ 16.62 \(U_{p_1 } \) for the two-color field of fundamental frequency and its third harmonic with equal intensities, which is in accordance with the results of classical analysis. The results of classical analysis of the ionization processes in the field of first and nth harmonics of equal intensities show that the length of the direct ionization plateau and the length of the high-energy rescattering plateau decrease with increasing n. The results of numerical analysis of the ionization processes in the field of first and third (n = 3) harmonics correspond to the results of classical analysis carried out by the authors.