  We develop a time-dependent theory to investigate electron dynamics and
photoionization processes of diatomic molecules interacting with strong laser
fields including electron-electron correlation effects. We combine the recently
formulated time-dependent generalized-active-space configuration interaction
theory [D. Hochstuhl and M. Bonitz, Phys. Rev. A 86, 053424 (2012); S. Bauch,
et al., Phys. Rev. A 90, 062508 (2014)] with a prolate spheroidal basis set
including localized orbitals and continuum states to describe the bound
electrons and the outgoing photoelectron. As an example, we study the
strong-field ionization of the two-center four-electron lithium hydride
molecule in different intensity regimes. By using single-cycle pulses, two
orientations of the asymmetric heteronuclear molecule are investigated: Li-H,
with the electrical field pointing from H to Li, and the opposite case of H-Li.
The preferred orientation for ionization is determined and we find a transition
from H-Li, for low intensity, to Li-H, for high intensity. The influence of
electron correlations is studied at different levels of approximation, and we
find a significant change in the preferred orientation. For certain intensity
regimes, even an interchange of the preferred configuration is observed,
relative to the uncorrelated simulations. Further insight is provided by
detailed comparisons of photoelectron angular distributions with and without
correlation effects taken into account.
