  In the present paper, we develop a semiclassical quasi-static model
accounting for molecular double ionization in an intense laser pulse. With this
model, we achieve insight into the dynamics of two highly-correlated valence
electrons under the combined influence of a two-center Coulomb potential and an
intense laser field, and reveal the significant influence of molecular
alignment on the ratio of double over single ion yield. Analysis on the
classical trajectories unveils sub-cycle dynamics of the molecular double
ionization. Many interesting features, such as the accumulation of emitted
electrons in the first and third quadrants of parallel momentum plane, the
regular pattern of correlated momentum with respect to the time delay between
closest collision and ionization moment, are revealed and successfully
explained by back analyzing the classical trajectories. Quantitative agreement
with experimental data over a wide range of laser intensities from tunneling to
over-the-barrier regime is presented.
