Comparison of Strong-field Ionization Models in the Wavelength-scaling of High Harmonic Generation

The output from a wavelength-tunable optical parametric amplifer was used to generate high-order harmonics in a range of nobel gases. The phase-mathcing pressure and harmonic cut-off were recorded for each target gas at diffenent fundamental wavelengths. The experimental results are compared to a model of the high-harmonic generation process, which include two separate models of photo-ionization. The calculated results using the Yudin-Ivanov model of ionization are shown to yield superior agreement with experiment in contrast to the more widely used Ammosov-Delone-Krainov model