Multielectron corrections in molecular high-order harmonic generation for different formulations of the strong-field approximation

We incorporate multielectron corrections due to exchange and electron-electron correlation in high-order harmonic generation of diatomic molecules in a static and analytic framework. These corrections were incorporated perturbatively around the highest occupied molecular orbital of aligned isoelectronic homonuclear and heteronuclear molecules, exemplified by N(2) and CO, respectively. This is performed for the velocity and length forms of the dipole operator within the framework of the strong field approximation. We find that inclusion of the multielectron corrections has very little effect on the spectrum. This suggests that relaxation, excitation and the dynamic motion of the core are important in order to describe multielectron effects in molecular high-order high harmonic generation. These features are not included in the present model and possibly enhance such effects.