Electron correlation versus stabilization: A two-electron model atom in an intense laser pulse

We study numerically stabilization against ionization of a fully correlated two-electron model atom in an intense laser pulse. We concentrate on two frequency regimes: very high frequency, where the photon energy exceeds both the ionization potential of the outer and the inner electron, and an intermediate frequency where, from a "single active electron" point of view, the outer electron is expected to stabilize but the inner one is not. Our results reveal that correlation reduces stabilization when compared to results from single active electron calculations. However, despite this destabilizing effect of electron correlation we still observe a decreasing ionization probability within a certain intensity domain in the high-frequency case. We compare our results from the fully correlated simulations with those from simpler, approximate models. This is useful for future work on "real'' more-than-one electron atoms, not yet accessible to numerical ab initio methods. [S1050-2947(99)06109-0].