Keldysh ionization theory of atoms: mathematical details
Neda Boroumand, Adam Thorpe, A. M. Parks, Thomas Brabec
Abstract
Abstract Keldysh ionization theory is one of the main pillars of strong field physics and attosecond science. It describes non-relativistic ionization rates of hydrogen-like atoms subjected to strong laser fields within the dipole approximation and the length gauge. According to this theory ionization can be described by two regimes: electronic tunneling through a laser-dressed atomic potential (tunnel ionization) and absorption of multiple photons at once (multi-photon ionization). There are many gaps in the mathematical steps and explanations in the original Keldysh paper. Therefore, the goal of this work is to give a detailed re-derivation of ionization rates following Keldysh’s formulation and to fill in the mathematical steps of this beautiful approach so that it is more accessible to a wider audience.