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An innovative beamline for small molecule chemical crystallography has been built at the Advanced Light Source. The system permits the study of crystals as small as 10µm x 10µm x 10µm. The beamline produces a 7-17 keV x-ray beam focused to a 280µm x 90µm spot. A channel-cut Si<111> monochromator and a toroidal mirror are inside the synchrotron shield wall only 7m from the bending magnet source point. The monochromator is cooled with a small Joule-Thomson refrigerator to produce a very small beam motion with different heat loads. The experimental hutch contains a vertically mounted sample goniometer and a CCD detector. An on-axis visual alignment camera allows the small crystals to be accurately centered within the x-ray beam. Examples of the crystal structures solved with this system are given. The beamline is also used for high-pressure powder diffraction experiments using a diamond anvil cell that is mounted on a stage system that can be quickly installed and removed.

Standard reference markers for accurate, reproducible synchrotron x-ray energies are obtained using a three Si crystal spectrometer. The first two crystals are in the monochromator and the third is used to obtain diffraction markers which monitor the energy. Then for any value of the glancing angle on the reference Si crystal the energy for the (333) diffraction must occur at 3/4 that of the (444) and 3/5 of that for the (555). This establishes for the first time an absolute synchrotron energy scale. Higher-order diffractions are used to determine excitation line profiles. We conclude that the use of reference diffractions is necessary to measure reproducible x-ray energies and to analyze the incident photons’ line profile. The detection of diffractions near the edge of measurement and near the Cu edge will provide a fast secondary standard which will allow comparison of edge data between different laboratories. The diffraction profiles will allow the proper analysis of spectral line widths.

In the LBNL x-ray fluorescence microprobe, a synchrotron source of x-rays is demagnified several hundred times using a pair of mirrors in the Kirkpatrick-Baez configuration. These are coated with multilayers to increase reflectivity and limit the pass band of the x-rays striking the sample. With spherical mirrors, the spot size obtained is limited by spherical aberration. This can be corrected by using an initially flat mirror elastically bent by a combination of end couples into an ellipse. By grading the multilayer coatings in d-spacing, the throughput of the focusing system is increased and the pass band narrowed. A pair of such mirrors, installed in the microprobe on a bending magnet at the Advanced Light Source (ALS), achieved focal spots of dimensions 1μm×1 μm at energies of 8.5 keV and 12 keV, with an energy pass band of 10%.

A Light Scattering Experiment for Physical Chemistry 1 t,r the past several years, light scattering experiments with commercial colloidal silica sols have been carried out by the authors and various students enrolled in the physical chemistry laboratory program. Another student (1). S.) wrote an IBM 1130 computer program for the calculation of dissymmetry corrections. Electron microscope pictures to compare with experimental results were provided by R. E. Crang (Wittenberg University, Dept, of Biology, Springfield, Ohio). The objective of these experiments was mainly pedagogical. Physical chemistry students were introduced to an important aspect of colloidal chemistry. It was hoped also that the results would have some value as research.

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