Enhanced narrow-bandwidth emission during high-order harmonic generation from aligned molecules

We theoretically investigate the selective enhancement of high-harmonic generation (HHG) in a small spectral range when an orthogonal-polarized two-color laser field interacts with aligned O(2) molecules. It is shown clearly that the enhanced narrow-bandwidth emission near the cutoff of the HHG spectrum can be effectively controlled by the molecular alignment angle, laser intensity and the relative phase of two-color laser fields. Furthermore, the strong dependence of narrow-bandwidth HHG on molecular alignment angle indicates that it encodes information about O(2) molecular orbitals, so it may be an alternative method for reconstruction of O(2) molecular orbitals.