Interaction of a two-electron system with an ultrashort laser pulse

We present two ab initio approaches to solving the time-dependent Schroedinger equation for two-active electron systems interacting with an intense laser pulse. The two approaches, which are relevant to the Configuration Interaction (CI) method, are based on an expansion of the wave function on either (real) B-splines or (complex) Sturmian functions for the radial part, and bipolar spherical harmonics for the angular part. Despite some convergence problems inherent to all CI methods, we show that it is indeed possible to treat the electron-electron correlation so as to provide an accurate description of the atomic structure. The time propagation of the state vector is performed in the atomic basis and within the interaction picture using explicit Runge-Kutta methods. As test cases, we consider the photodetachment of H- and display the dynamics of a Rydberg wavepacket in helium