Turning point behaviour in tunnel ionization of atoms in super-strong, low-frequency laser fields

In the case of the short-range potential [1,5,8,9], the estimation of the probability of ionization of atoms is carried along taking into account the approximation (Keldysh approximation) which states that this kind of potential does not affect the energy of the final state f of the ejected electron in the laser field, because the electron is far enough from the nucleus. When the Coulomb potential is taken into account, it can be treated as a perturbation to the energy of the final state [1,10]. Yet, originally [1,10], the Coulomb potential in this kind of estimation was not included into calculating the turning point. This was done in [7], but only for the fields below the atomic field (10(16) W/cm(2)). Now, based on the results [11,12], we are extending our calculation that included the Coulomb correction into the estimating the turning point to the fields that are much stronger (up to 10(17) W/cm(2)). That results in the shift of the position of the turning point tau. This paper is dealing with the influence of that shift on the ionization probability for atoms in the low-frequency electromagnetic field of superstrong lasers.