Calcium L-edge XANES study of some calcium compounds.

The Ca L3,2-edge XANES spectra of six calcium salts have been measured in both total electron and fluorescence yields using a high-resolution spherical grating monochromator. The compounds investigated were; CaF2, CaCO3, CaCl2 x 2H2O, calcium phosphate, calcium glycerophosphate and calcium gluconate. We find that the fine structure of the Ca L3,2-edges for each compound is unique and relates to the local structure of the Ca atom. The implications of these results to the study of the structure of calcium binding sites in systems of biologically interest will be discussed.

Two-photon resonant upconversion in xenon.

Coherent radiation at various VUV wavelengths, e.g., 125.9, 126.1, and 125.4 nm, has been generated through fourwave mixing processes enhanced by two-photon resonances in xenon. Maximum efficiencies of the order of 10(-4) were achieved. Maximum output intensities of difference generation (2omega(1) - omega(2)) for 7p[0 (1/2)](0), 7p[1 (1/2)](2), and 6p' [1 (1/2)](2) resonant states occurred at xenon pressures of 24, 12.5, and 4 Torr, corresponding to values of phase mismatch per atom of 1.2 x 10(-18), 2.3 x 10(-18), and 7.1 x 10(-18) esu, respectively. Parametric generation at 117.0 nm through the 7s[1(1/2)](0)(1) state was also observed.

Generation of Lyman-alpha radiation in phase-matched rare-gas mixtures.

When frequency tripling to Lyman-alpha in Kr, we find a Kerr-induced index mismatch per atom of gamma Kr = -5.6 X 10(-36) esu, which dominates the dispersion for power densities exceeding 4 X 10(12) W/cm2 . Results of phase matching Kr with Ar and Xe are presented. Dielectric breakdown provides a limitation that, when combined with a requirement of a 1-A bandwidth at Lyman-alpha, indicates that powers of a few kilowatts are achievable in a Kr-Ar phase-matched medium.