The advent of ultra-high intensity (table-top) laser sources, makes
possible the observation of highly non-linear effects, some of them
involving relativity, in atom-laser interactions.
The dominant effects originate from the fact that an atomic
electron in the presence of an ultra-strong laser field
can experience a significant mass shift and can acquire relativistic
velocities as its ponderomotive
(quiver-) energy can become comparable to its rest mass.
Moreover, when an isolated atom is exposed to
an ultra intense pulse of an infrared laser, it is admitted that
the outer shells of the atom will be at once ionized. Under such
extreme circumstances, it is expected that
the response of a low density sample of atoms will be dominated by
the relativistic dynamics of the electrons within the laser
field. It appears however that the
dynamics of atomic ionization affects significantly the spatial
distribution of
the ejected photoelectrons.
We shall comment several issues related to this question as well
as to other topics such as the radiative processes
experienced by electrons in the presence of the laser field.
Present address: Rochester
Theory Center for Optical Sciences
and Engineering, Department of Physics and Astronomy,
University of Rochester. Rochester, NY 14627 USA.