Keldysh theory of strong-field ionization

摘要

In this paper, we provide a detailed derivation of the strong-field ionization rates originally developed by Keldysh who introduced the strong-field approximation. Numerical results are presented to examine the saddle-point approximation, the low photoelectron energy approximation, and neglecting the interference terms, which are necessary to arrive at the simple quasistatic result, when the Keldysh parameter becomes very small.