Tunneling limit in the theory of photoelectron rescattering by the parent ion

A generalized Keldysh model is used to obtain simple analytical expressions for the energy and angular distributions of photoelectrons rescattered by the parent ion. The dependence of the form, absolute magnitude, and interference structure of the distributions on the parameters of the field and atom is investigated. It is shown that even though the semiclassical three-step rescattering model determines correctly the position of the boundaries beyond which the distributions decay rapidly, the model itself is inapplicable near them.