The study of the response of a two-active electron system exposed to an intense
laser pulse represents a tremendous task from the theoretical point of view.
To tackle this problem, we have analysed various coordinate systems and
appropriateness, having in mind a good description of the physics of the
problem as well as the numerical resolution of the corresponding
time-dependent Schrodinger equation.
We have singled out one particular coordinate system and presented in this
thesis detailed results about the field free energies, oscillator strengths,
Rayleigh and Raman
(from the ground state and the first excited state).
We present also an original method to treat One and Two colour photoionization
of helium problems.
This method consists in solving numerically the time-dependent
Schrodinger equation for a few discrete complex eigenstates obtained by
complex scaling of the atomic and interaction Hamiltonians.
The results, obtained for the study of the
with exitation of an intermediate autoionizing state, show
a Autler-Townes splitting of this intermediate autoionizing state at low
intensities of the second laser.