Wavelength effect on atomic and molecular high harmonic generation driven by a tunable infrared parametric source

We experimentally investigate the wavelength effect on highorder harmonic generation (HHG) in CH₄ molecules and Xe atoms driven by a tunable infrared parametric source, and observe that the molecular HHG around the vibrational resonance is more sensitive to the driver wavelength than HHG from an atomic gas with comparable ionization potential. The results can be attributed to the light nuclear motion induced by the driving laser field, and it becomes possible to control the proton vibration in the molecular HHG by tuning the infrared wavelength of the driving laser.