Above-threshold ionization of hydrogen atoms in a two-color laser field

By using the method of electron wave packet interference, we investigate the above-threshold ionization (ATI) of hydrogen atoms in a linearly polarized two-color laser pulse (λ ₁ = 800 nm and λ ₂ = 400 nm). Firstly, using the strong field approximation (SFA) with the time window function, we obtain the intracycle interference and intercycle interference patterns of hydrogen atoms in a 10 fs laser pulse, and it is found that the general characteristics of two-dimensional photoelectron momentum spectrum are formed by the interplay of the intracycle interference and intercycle interference, and the side rings in two-dimensional photoelectron momentum spectra originate from intercycle interference. Subsequently, we calculate the two-dimensional photoelectron momentum spectra of hydrogen atoms by SFA in full pulse. When the relative phase ϕ = 0, the intracycle interference and intercycle interference fringes in two-dimensional momentum spectrum are symmetrical, and when the relative phase is ϕ=0.5π, the intracycle interference fringes in the two-dimensional momentum spectrum are obviously asymmetrical. The results show that ionization is vitally dependent on relative phase of two laser pulses in two-color laser filed. (paper)