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".