Ionization suppression of diatomic molecules in different wavelength laser fields

We theoretically study ionization of the N2 and O2 molecules and focus on the ionization suppression at various wavelengths. We find that the ionization rate of the N2 molecules is not significantly suppressed over a wide range of laser wavelengths. The ratio of the ion yields of N2+ to that of Ar+, however, slightly decreases as the laser wavelength increases, and this ratio for the low laser intensity is slightly larger than that for the high laser intensity. The interference effect greatly modulates the photoelectron energy spectra: an interference valley appearing in the photoelectron energy spectra. For the O2 molecules, the ionization suppression is always significant, and clearly depends on the laser wavelength and the laser intensity. The ratio of the ion yields of O2+ to that of Xe+ becomes larger as the laser wavelength (intensity) increases under given laser intensity (wavelength). Overall photoelectron energy spectra of O2 are suppressed, especially for the low-energy range.