HIGH-ORDER HARMONIC-GENERATION AND IONIZATION USING ULTRASHORT KRF AND TI - SAPPHIRE LASERS

High-order harmonic generation with KrF and Ti:sapphire lasers is anal yzed with an emphasis on contribution of multiply charged ions. It is confirmed that the intensity dependence of strong optical field ioniza tion is explained by the Ammosov-Delone-Krainov (ADK) theory or by the barrier suppression ionization model regardless of the wavelength. Th e harmonic distributions are compared with the single-atom responses c alculated using the short-range potential model with the effective int eraction intensity determined by the ADK theory. From this analysis, w e propose that for the KrF laser the harmonics above the 2 1 st in Ne and above the 13th in Ar may be due to doubly charged ions.