Tunneling and above-barrier ionization of atoms in a laser radiation field

Calculations are made of the energy and angular distributions of photoelect rons during tunneling ionization of an atom or an ion under the action of h igh-power laser radiation (for all values of the Keldysh parameter gamma). Cases of linear, circular, and elliptic polarizations of the electromagneti c wave are considered. The probability of above-barrier ionization of hydro gen atoms in a low-frequency (gamma much less than 1) laser field is calcul ated. Formulas are given for the momentum spectrum of the electrons when an atomic level is ionized by a general type of alternating electric field (f or the case of linear polarization). An analysis is made of tunneling inter ference in the energy spectrum of the photoelectrons. Analytic approximatio ns are discussed for the asymptotic coefficient C-kappa of the atomic wave function at infinity (for s-wave electrons). (C) 2000 MAIK "Nauka/Interperi odica".