Energy and momentum spectra of photoelectrons under conditions of ionization by strong laser radiation (the case of elliptic polarization)

Analytical and numerical studies are made into the momentum distribution and energy spectra of photoelectrons emitted during nonlinear ionization of atoms and molecules by laser radiation with elliptic polarization. The dependence of these distributions on the ellipticity xi of an electromagnetic wave is treated, as well as their evolution upon variation of the Keldysh parameter gamma from the region of optical tunneling (gamma << 1) to the region of gamma >> 1, in which the ionization is multiphoton. The quasiclassical approximation is used in the calculations, in particular, the imaginary-time method and the saddle-point method with expansion in the vicinity of the field ellipse. (C) 2001 MAIK Nauka/Interperiodica.