, Volume 20, Issue 3, pp 573-580
Date: 02 Feb 2010

Low-frequency approximation for high-order above-threshold ionization

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The low-frequency approximation (LFA) for high-order above-threshold ionization is presented. A factorization formula for the differential ionization rate is derived and its range of validity is analyzed. The theory developed is illustrated using the example of Ar atoms. Details of the modeling of the ground state and the rescattering potential for Ar are given. In particular, it is shown, by solving the stationary Schrödinger equation, that our rescattering potential reproduces the Hartree—Fock-type ground-state wave function that we used for the LFA. Electron momentum distributions for ionization of the Ar atom by a linearly polarized laser field having intensity 2.3 × 1014 W/cm2 and wavelength 800 nm are shown. The results obtained using the improved strong-field approximation on the one hand and the LFA on the other are compared.