Improved treatment of the turning point in tunnel ionization of atoms in a low-frequency electromagnetic field

Abstract

In constructing the ADK theory, the Coulomb interaction was not included as the first-order correction into the all phases, i.e., the turning point was calculated to the zero-order degree of approximation with regard to the Coulomb interaction. This was correct for fields (up to 1012 W/cm2 ) much smaller than the atomic field (1016 W/cm2 ). But as lately in experiments are used fields even greater than the atomic one (in this case ADK theory does not work), we decided to reconsider the influence of the Coulomb interaction on the turning point for the fields that are strong enough to make a difference and yet are smaller than the atomic fields (i.e.,for fields of order of magnitude of 1014 W/cm2). So, in this paper we have included the Coulomb interaction where it has been completely neglected earlier. We have shown that this more accurate approach gives somewhat different result for the ionization probability.