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Instrumental Chemistry

Instrumental Chemistry. Chapter 12 Atomic X-Ray Spectroscopic. Brief Summary. X-ray spectroscopy is a form of optical spectroscopy that utilizes emission , absorption , scattering , fluorescence , and diffraction of X-ray radiation. About X-Rays.

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Instrumental Chemistry

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  1. Instrumental Chemistry Chapter 12 Atomic X-Ray Spectroscopic

  2. Brief Summary X-ray spectroscopy is a form of optical spectroscopy that utilizes emission, absorption, scattering, fluorescence, and diffraction of X-ray radiation

  3. About X-Rays • X-rays are short-wavelength (hence, high frequency, and hence, relatively high energy) electromagnetic radiation. Two ways to produce X-rays: 1) Deceleration of high-energy electrons 2) Electronic transitions involving inner-orbital (e.g. - d or f) electrons

  4. For analytical purposes, X-rays are generated in three ways: 1) bombardment of metal target with high-energy electron beam 2) exposure of target material to primary X-ray beam to create a secondary beam of X-ray fluorescence 3) use of radioactive materials whose decay patterns include X-ray emission

  5. Schematic of an X-ray tube

  6. Energy-level diagram showing common transitions producing X-rays

  7. Electron beam sources In electron beam sources, X-rays are produced by heating a cathode to produce high-energy electrons; these electrons are energetic enough to ionize off the cathode and race towards a metal anode (the target) where, upon collision, X-rays are given off from the target material in response to the colliding electrons.

  8. TheDuane-Huntlaw The maximum photon energy corresponds to total stopping of the electron and is given by: hvo = (hc)/o = Ve vo is the maximum frequency V = accelerating voltage e = electron charge

  9. X-ray Fluorescence Since X-rays are rather energetic, excitation of sample electrons will give rise to fluorescence as the sample electrons are excited and return to their ground states in a series of electronic transitions.

  10. Bragg equation sin  = (n)/2d = angle of incidence  = wavelength d = interplane distance of crystal

  11. Diffraction of X-rays by a crystal

  12. X-ray monochromator and detector

  13. References http://www.anachem.umu.se/jumpstation.htm http://userwww.service.emory.edu/~kmurray/mslist.html http://www.chemcenter/org http://www.sciencemag.org

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