Strong field ionization of many electron systems: A quantum chemical challenge

A non-variational Time-Dependent Multiconfiguration Self-Consistent Field (TDMCSCF) scheme has been developed [Nguyen-Dang T.T., Peters M., Wang S.-M., Sinelnikov E., and Dion F., J. Chem. Phys. 127, 174107 (2007)] to describe, by an ab-initio approach, the time-resolved electron dynamics of a laser-driven many-electron atomic or molecular system. As an L (2) method, this approach faces severe challenges when ionization and large-amplitude electronic motions are addressed. We present here an extension of this TDMCSCF scheme to include multiple ionization processes, using a Feschbach state-partitioning formalism, allowing the bound electrons' dynamics to be treated by the L (2)-TDMCSCF method, while the ionized electrons can be treated separately by an alternative approach. We present results of proof-of-principle calculations pertaining to the single and double ionizations of H (2) and discuss methodological issues such as the systematic corrections that could be brought, using this approach, to the strong field approximation (SFA).