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Abstract. [Na(C6H4NO3)].2H20, Mr = 197.12, orthorhombic, lma2, a=6.892(1), b = 19.692(2), c = 6.439 (1)/k, V= 873.8 (1) A, 3, Z = 4, Ox = 1.498 g cm -3, A(Cu Kge) = 1.5418/~,, /z = 15.1 cm-1, F(000) = 408, T = 295 K, R = 0.066 for 357 observed reflections. The p-nitrophenolate molecule, as well as the Na cation, is located on the crystallographic mirror plane. The Na cation is in contact with four O atoms, the distances being between 2.32 and 2.66 ~,. The solvated water molecule is hydrogen bonded to the two O atoms of the NO2 group. 0108-2701/92/040737-02503.00 044, 400) were remeasured every 60 reflections, no significant loss of intensities was observed. 663 reflections were collected with 20 up to 116 ° (sin0/a = 0.550 A-1) and an index range of h = 0 to 7, k = 0 to 21, l = -7 to 7. By averaging Friedel-pair reflections, 367 independent reflections were obtained (Rin t = 0.010). Corrections for Lorentz and polarization effects were applied, while neither absorption nor extinction corrections were carried out.The structure was solved by direct methods using SHELXS86 (Sheldrick, 1986)

Detailed characterization using x-ray diffractometry, scanning electron microscopy, transmission electron microscopy, x-ray photoelectron spectroscopy, and Auger infrared and focused ion-beam spectroscopy, was carried out on cubic SiC films grown on single-crystal (100) Si substrates by reactive hydrogen plasma sputtering over a range of growth temperatures between 700 and 1000 °C. It was found that the first few deposited atomic layers were always amorphous. The subsequent SiC films showed well-defined (111) growth at the lowest temperatures, becoming randomly oriented by 1000 °C. The measured C:Si ratio was always >1, and varied with depth inside a film and also with temperature. At higher temperatures, the presence of “hollow voids” was observed, our data being consistent with their formation by outdiffusion of Si atoms from the substrate through the SiC layer. Associated with the hollow voids we observed the presence of a porous, highly C-rich region at the Si–SiC interface. We propose that this was due to diffusion of C from the SiC film into the voids themselves.

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The fluorescence spectra of 7-azaindole show a dramatic red shift during the gel-xerogel stages, revealing that 7-azaindole is an excellent photophysical probe for gel-xerogel transition. This large shift in fluorescence is due to stabilization in the excited state, which is probably induced by a specific interaction between 7-azaindole and silanol groups, which are surrounded by a large number of polar silanol groups. Tautomeric fluorescence, due to double proton transfer, is thought to occur in the xerogel as well as the starting solution and the gel. Further study of this material system will clarify the microstructure of silica cage, the interaction between 7AI and silanol groups, and the mechanism of double proton transfer.