mosphere. The graphite cathode of 10 mm diameter was placed horizontally facing the composite anode of 6.15 mm diameter. The latter had a 3.2 mm diameter hole drilled 25 mm filled with a mixture of graphite (Graphit, fein gepulvert reinst, Merck, Germany) and Si powder in the atomic ratio 1:1.The experiments were repeated with and without the addition of 0.03 at.-% of Fe powder to the anode. During arc-discharge evaporation of the graphite/ silicon composite anode a hard cylindrical deposit (the core deposit) grows at the end of the graphitic cathode. Additionally a soot-like deposit is formed around the core deposit of the cathode, here called the collaret deposit. Samples for TEM examination were prepared from the core deposit as well as from the collaret deposit. The deposits were diluted in chloroform, sonicated for 5 min and dropped on a TEM Cu grid (300 mesh) with holey carbon film.The characterization of the samples was performed using TEM, HRTEM, electron diffraction, and analytical electron microscopy using EELS.TEM was carried out with a JEM 2000FX (JEOL, Japan), using an acceleration voltage of 200 kV, HRTEM was carried out with a JEM 4000EX (JEOL, Japan), using an acceleration voltage of 400 kV, and EELS was carried out with a PEELS 666 (Gatan, USA) on a dedicated STEM VG HB 501 UX (Vacuum Generators, UK) operating with a cold field emission gun at 100 kV acceleration voltage. All EELS data were acquired and processed using the EL/P 3.0 software (Gatan, USA). Pure Si and SiC powder samples prepared for electron microscopy in the same way as the arc discharge products were characterized by EELS in order to get reference spectra acquired under comparable conditions.The Si-L edges were acquired with an energy dispersion of 0.1 eV, a convergence angle of 10 mrad and a collector angle of 6.5 mrad. For the measurement of the Si-K edge the gun-lens was less excited to get a sufficient electron intensity at energy losses of about 1800 eV; the energy dispersion was adjusted at 1.0 eV. The Si-K edges were measured with a convergence angle of 10 mrad and a collector angle of 13 mrad.The energy location of the Si-L and the C-K edges was calibrated using zero-loss spectra acquired before the measurements. As a result the error of the energy location is less than ±0.2 eV. A deconvolution of the low-loss spectra was performed to remove the effect of sample thickness on the ELNES of the spectra.

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Experimental3T:bCD (pale yellow solid, 13 % yield): 3T (104.2 mg, 7 mM) was added to a saturated bCD solution (608 mg, 10 mM, at 20 C). The mixture was stirred at 95 C under Ar for 6 h, then allowed to cool at room temperature. The precipitate was isolated by filtration, washed with water and ether, then dried under vacuum for 4 h. Elemental Analysis Calcd. for C 54 H 78 O 35 S 3 × 5H 2 O : C 44.02, H 5.98, O 43.48, S 6.52; found, C 44.02, H 6.04, O 42.10, S 5.94.UV-vis and fluorimetric experiments were performed, respectively, on a Perkin Elmer lambda2 spectrophotometer and on an Aminco-Bowman series 2 luminescence spectrometer equipped with a thermostated cell carrier. The apparatus for the FTIR experiments is described elsewhere [22]. Chemical ionization (CI) mass spectrometry was performed using a triple±quadrupole tandem mass spectrometer (R30-10 Nermag). The sample was introduced into a high-pressure ion source by using a direct desorption chemical ionization (DCI) probe and heating the tungsten filament. The mass spectrum corresponded to an average of 30 full spectra recorded on an EZ-SCAN acquisition system. The following source operating conditions were used: electron energy, 85 eV; emission current, 100 mA; repeller, 0 V; pressure of ammonia as reagent gas, »10 ±4 torr in the source housing (measured above the secondary pumping).

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We demonstrate optical storage by means of trans-cis isomerization within melamine monomers as well as within the corresponding cross-linked melamine resins using holographic grating experiments. The melamine monomer is chemically linked with a photoaddressable azobenzene group. By thermal treatment the semicrystalline monomers can be converted into the amorphous cross-linked resin. Both the monomer material and the cross-linked resins display a photoinduced trans-cis isomerization of the azo groups, a stable photoorientation under irradiation with linear polarized light, and a stable storage of holographic gratings. The photokinetics in the different environments are found to be similiar but somewhat faster for the amorphous resins.