Dressed-bound-state molecular strong-field approximation: application to high-order harmonic generation by heteronuclear diatomic molecules
A theory of high-order harmonic generation by heteronuclear diatomic molecules exposed to an elliptically polarized laser field is presented. This theory is based on the molecular strong-field approximation, which takes into account the dressing of the initial and final molecular bound states caused by the laser field. The laser-field-caused Stark shift of the effective ionization potential of the highest occupied molecular orbital changes the structure of the harmonic spectra. Both the even and odd harmonics appear in the harmonic spectra due to the broken inversion symmetry of the heteronuclear diatomic molecule. An interference minima condition that is valid for arbitrary heteronuclear diatomic molecules is derived. Our results are illustrated using examples of CO and NO molecules.