“…The dependence of the seventh-harmonic intensity and other characteristics obeyed classical nonlinear optics. 3 The output was limited by ionization, which decreased the number density of the nonlinear medium and deteriorated the phase matching. We treated the short-pulse VUV emission as a seed pulse for the optical-field-induced ionization (OFI) VUV Ar 2 * (argon dimer) amplifier.…”