HIGH RESOLUTION SINGLE CRYSTAL DIFFRACTION USING SYNCHROTRON RADIATION H. Graafsma, O. Svensson, A. Kvick, European Synchrotron Radiation Facility, BP 220 38043 Grenoble, France

The advantages of synhrotron radiation for high resolution single crystal diffraction, e.g. for electron density distributions,are well known [1]. The high energies reduce systematic errors such as absorption and primary extinction. The same is achieved by using small samples, possible due to the high flux at the sample. This high flux also permits the measurement of higher order data, as well as weak reflections [2]. An other advantage beside accuracy is the high speed. The combination of 2D-detectors and the high flux at the sample allows to record a full data set within hours. The results of two measurements at 56 keV (0.22 Å), performed at the materials science beamline of the ESRF will be presented. The first is the determination of the electron density of Magnesium Formate Dihydrate, using a Princeton Instruments slow scan CCD coupled to an Image Intensifier. The second is an electron density study of Amonium Dihydrogen Phosphate (ADP) using the SIEMENS SMART system. Both measurements gave an R-int of the order of 3%, with data extending to sin(th)/l=1.4. The first data set was measured in 2 hr, using an oscillation per frame of 4 degrees. The data was integrated both with DENZO and the Seedskewness package. The second data set was obtained in 9 hours using an oscillation of 0.05 degrees per frame, and integrated with the SIEMENS SAINT program using 3-dimensional profile fitting.

[1] Synhrotron Radiation Crystallography; P. Coppens, Academic Press Limited, 1992.

[2] A. Kirfel and K. Eichhorn, Acta Cryst. A46,271 (1990).