Anisotropic Kα X-ray production by 350 keV electrons in germanium single crystals

Bombarding thin single crystal films with electrons an increase of K X-ray yield is observed if a crystallographic axis or plane is rotated into the beam direction. In the case of epitaxial foils the shape of the yield peaks is of Gaussian type and the width is larger than twice the Bragg-angle depending strongly on target preparation. We have investigated these peaks around the [111] axis of a germanium single crystal thinned by ion-sputtering to a thickness of about 1 pm. An exact agreement of the width with twice the Bragg-angle and a fine structure related to the Kikuchipattern was observed.     

neue Heterocyclisierungen mit Malonestern 1,3-Dithiole; 1,3-Oxathiole; Δ2-Oxazoline und das Vinylendipyridiniumdikation

The reaction of diethyl bromomalonate (1) or diethyl diazomalonate (6) with benzoyl isothiocyanate (2) proceeds via the carbene intermediates4, 7 or12 to afford the 1,3-dithiole5, the 2-oxazoline8 or the 1,3-oxathioles9 depending upon the catalyst employed. In contrast, the bis(ethoxycarbonyl)methylpyridinium bromides14 upon treatment with benzoyl isocyanates15 in pyridine give rise to vinylene dipyridinium dibromides18.