The time evolution of the reduced single electron density matrix for eight electrons in a one-dimensional finite box potential driven by an intense laser field is calculated by numerically integrating the time-dependent Hartree-Fock equations. We study the effects of the Coulomb interaction, field intensity, and frequency on the time profile of the ionization process. Our computed saturation ionization intensity (I-sat) is in good agreement with experimental results for decatetraene [Ivanov J. Chem. Phys. 117, 1575 (2002)]. (C) 2004 American Institute of Physics.