Modeling of strong-field processes in many-electron systems presents a formidable computational challenge. Ab initio treatments of such systems have so far been limited to at most two electrons and/or low-dimensional models. Larger problems of practical interest are usually treated with model one-electron Hamiltonians. We have recently proposed a new approach [1] for ab initio simulation of electron dynamics of molecules in atoms in molecules. The technique is based on: a) use of non-antisymmetric "proxy" wavefunction and b) expansion in the mixed N/(N-1)- electron basis of the neutral molecule and (possibly several) ion states. The effects of molecular potential on the continuum and correlations between the bound and continuum electrons are treated, permitting realistic simulations of electron dynamics in strong laser fields. We present some initial results obtained with the new technique, including angular-resolved ionization yields in strong fields and high-harmonic spectra of polyatomic molecules.
[1] M. Spanner and S. Patchkovskii, Phys. Rev. A 80, 083411 (2009)