Few-body dynamics in ultrashort laser pulses

We present a model for ab-initio calculations of the interaction of two-electron atoms and molecules with few-cycle pulses of intense linearly polarised Ti:sapphire laser radiation. In the model the center-of-mass motion of the two electrons is restricted along the polarisation direction axis, while its relative coordinate and, hence, the electron correlation is retained in its full dimensionality. Results of numerical simulations exhibit the two pathways to nonsequential double ionization, namely the emission of a highly correlated electron pair upon rescattering and a delayed electron emission from a previously excited ion. Comparisons with the results of the usual one-dimensional approximation, in which the direction of each electron is restricted to the polarisation axis, are given. Distributions of the center-of-mass momentum and the correlated electron momenta along the polarisation direction are in qualitative agreement with the experimental data.