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. The Duane-Hunt law The maximum photon energy corresponds to total stopping of the electron and is given by: hv o = (hc)/ o = Ve v o 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.ht m http://userwww.service.emory.edu/~kmu rray/mslist.html http://www.chemcenter/org http://www.sciencemag.org