Ionization of atoms in the tunnelling regime with experimental evidence using Hg atoms

Abstract

Some 'Keldysh-like' theories are analysed leading to a more pragmatic definition of the tunnelling regime of ionization of atoms. Rather than using the more extreme definition of tunnelling (i.e. gamma <at), a more precise definition of the Keldysh gamma parameter ( gamma (0.5) and of the laser field F (F(F_BSI) is proposed, where F_BSI is the barrier suppression ionization field. New experimental results of the ionization of mercury atoms by an intense CO₂ laser pulse are presented. This experiment, along with some previous experiments, have been analysed, and may be classified as tunnel ionization under this definition.