Analyzing the transition rates of the ionization of atoms by strong fields of a CO₂ laser including nonzero initial momenta

Abstract

Here, the method of including nonzero initial momenta for ejected electrons in strong infrared laser fields is further developed [8]. It has been shown that, apart from being natural, including the nonzero initial momenta enables one to go into a deeper analysis of the process of tunnel ionization of atoms in strong laser fields (intensity up to 10¹⁶ W/cm²). This is due to looking closely at Fig. 2, which indicates that all electrons that could be ejected, under the circumstances, are ejected at a field intensity ∼10¹³ W/cm², and that the effect of ionization after that is strongly diminished, which can be seen from the slope of the plates on Figs. 2 and 4. This also explains the saturation effect for fields up to 10¹⁶ W/cm² [1, 4, 5, 7], and probably this saturation goes on until the fields raising relativistic effects ∼10¹⁸ W/cm² [7]. Opposite to what was believed earlier [7], the atomic field intensities could be increased to values over 10¹⁷ W/cm² only when more than 10 electrons are ejected from the atom, it is shown that the properly calculated ionization of 9 electrons increases the atomic field intensity to ∼10¹⁸ W/cm².