Double ionization of excited helium states by an intense laser field: spin and dressing effects

We present numerical simulations for a model one-dimensional two-electron atom subjected to an intense laser pulse. Double ionization probabilities are presented when the atom is initially in an excited state and depend strongly on the spin state of the system. In view of the recollision picture, we show that they are strongly correlated with the electron-impact ionization probabilities. Furthermore, we show that the dressing by the laser of the remaining ion has to be taken into account to quantitatively describe the two-electron ejection in the low intensity range.