Relativistic generalization of the keldysh ionization theory

摘要

A relativistic generalization is proposed for the quasi-classical theory of the multiphoton ionization of atoms and ions in the presence of a high-intensity electromagnetic wave. The elliptical polarization of laser radiation is considered. Using the method of imaginary time, we find the subbarrier trajectory satisfying the classical equations of motion along which the electron tunneling takes place. The exponential factor in the ionization probability is calculated for an arbitrary adiabaticity parameter gamma, energy of level E-0, and a radiation ellipticity rho. An asymptotically accurate formula for the ionization rate of the atomic s level that involves the Coulomb, spin, and adiabatic corrections and the preexponential factor is derived for the low-frequency (gamma 1) laser radiation. It is demonstrated that, in the limit E-0 -> mc(2), the results obtained are transformed into the formulas of the nonrelativistic Keldysh ionization theory. Numerical estimates show that the relativistic corrections to the ionization probability are significant in the case of multicharged ions with Z (.) 40-60 at intensities of no less than 10(22)-10(23) W/cm(2).