BRAGG DIFFRACTION MEASUREMENTS ON CORUNDUM USING SYNCHROTRON RADIATION. C.G van Beek*, H.P Weber, P.Pattison and B.M. Craven*. *Department of Crystallography, University of Pittsburgh, PA 15260; Universite de Lausanne, CH-1015, Lausanne, Switzerland.

Data were collected at the Swiss Norwegian Beam Line at the ESRF. A spherical crystal of Corundum with diameter 0.20mm, as supplied by Sandoz Fils S.A., was used to collect Bragg diffraction intensities. Intensities were collected at wavelength of 0.5500 Angstrom using a Huber 6 circle diffractometer.

At room temperature, 5409 intensities were collected in an omega scan technique. The intensities covered a hemisphere in reciprocal space ranging from 0.70 up to 1.70 reciprocal Angstroms.

During the data reduction it was suspected that 222 reflections were affected by `umweganregung'. Additional measurements on several of these affected reflections clearly shows the characteristics of `umweganregung'. Rejecting these 222 reflections from the data gives 841 unique reflections with an internal agreement of R ( I ) = 0.030.

Additional data on the same crystal has been collected at room temperature at different wavelengths. A full sphere of reciprocal space was collected at a wavelength of 1.0000 Angstrom. The data at this wavelength consists of 2988 intensities going up to 0.95 reciprocal Angstroms. Additionally an hemisphere of reciprocal space was collected at a wavelength of 0.4000 Angstroms. The 1050 measured intensities at this wavelength cover reciprocal space up to 1.40 reciprocal Angstroms

Data will be analyzed by Mark Spackman, University of New England, Armidale, NSW 235, Australia.