NONLINEAR GENERATION OF EXTREME-ULTRAVIOLET RADIATION IN ATOMIC-HYDROGEN USING ELECTROMAGNETICALLY INDUCED TRANSPARENCY

Sum-frequency generation enhanced by electromagnetically induced trans parency (EIT) has been extended to the production of extreme ultraviol et (XUV) radiation in the range 97.3-92.6 nm from np-ls transitions (n = 4-8) in atomic hydrogen. Pulsed radiation Was generated by strong c oupling of the np and 2s levels with laser radiation at Balmer wavelen gths, and simultaneously (weaker) coupling of the 2s and Is levels by two-photon resonance with 243-nm laser radiation. Investigations were carried out over a range of laser intensities and products of interact ion length and atomic density (NL). As the product NL increased, the X UV intensities were greatly enhanced by EIT, and at high NL values, th e spectral distributions of some of the generated signals were found t o be distorted by the presence of molecular hydrogen. Calculated profi les, modified to incorporate the effects of nearby molecular resonance s, were shown to be in good agreement with the observed spectra.