Dressing and high-order harmonic generation in small molecules

The strong-field approximation was recently extended to take into account the effect of vibrational motion and laser-induced coupling of the Born-Oppenheimer states on high-harmonic generation in molecules. We present detailed calculations of the harmonic spectra in H2 and D2 for long laser wavelengths (2000 nm), comparing the effects of the dressing to the case of 800 nm. The main effect of dressing is an overall reduction of the harmonic generation and, at long wavelengths, a non-negligible change in the ratio of harmonic signals from different isotopes