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NSLS

NSLS. fluorescent screen (YAG crystal) and reflection mirror. SSD/ CCD detector. Motor driven incident slits (define the incident x-ray beam size). CCD camera Video camera. upstream beam aperture. 2 nd mirror. Long working distance microscope (10X).

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NSLS

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  1. NSLS fluorescent screen (YAG crystal) and reflection mirror SSD/CCD detector Motor driven incident slits (define the incident x-ray beam size) CCD camera Video camera upstream beam aperture 2nd mirror Long working distance microscope (10X) sample cell assembly and cubic anvil press (DIA) double crystal monochromator Synchrotron x-ray

  2. Symmetry

  3. Symmetry operation Rotation Mirror reflection Translation Inversion Symmetry element Rotation axis Center of inversion Mirror plane Vector

  4. Other (complex) symmetry elements Rotation Inversion Reflection Translation Rotation --- Roto-inversion axis xxx Screw axis Inversion --- --- xxx xxx Reflection --- --- --- Glide plane Translation --- --- --- ---

  5. Classification of symmetry elements 1 Proper symmetry elements improper symmetry elements Rotation axis Inversion center Translation axis Reflection plane Screw axis Inversion axis Glide plane (do not change shape) (involve shape change)

  6. Classification of symmetry elements 2 Finite symmetry elements Infinite symmetry elements Rotation axis Translation axis Inversion center Screw axis Reflection plane Glide plane Inversion axis (Result in finite number of objects) (Result in infinite number of objects)

  7. Finite symmetry operations Crystallographic Rotation axis N = 1, 2, 3, 4, 5, 6, 7…

  8. Homework3: (due on Oct. 31) • Assuming the following facilities are available: • sealed x-ray tube source, curved position sensitive detector, radius 150 mm. • sealed x-ray tube source, Bragg-Brentano goniometer, radius 200 mm, scintillation detector. • rotating anode source, Bragg-Brentano goniometer, radius 285 mm, scintillation detector. • sealed x-ray tube source, Bragg-Brentano goniometer, radius 250 mm, cooled solid state detector. • Synchrotron x-ray facility, Bragg-Brentano goniometer, radius 100 to 500 mm, cooled solid state detector. • 1.If you are to collect powder diffraction data with high resolution, what is the order of these five facilities should you choose? • 2.If you have 20 different samples to identify using x-ray diffraction and each facility charges you base on the time used, which facility should you choose (excluding synchrotron facility)?

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