ElectronDiffraction - Electron Diffraction Equipment:...

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Electron Diffraction Equipment: Electron diffraction tube (4 units); make sure special red cable is connected KV power supply & Banana plugs Ruler Purpose: The purpose of this experiment is to demonstrate the wave nature of matter. Background: Diffraction through a grating and the subsequent interference pattern is undeniably a property of waves. Therefore, if we observe a diffraction pattern resulting from interference of electron waves, we must conclude that some sort of maniacal channeling is taking place or electrons truly have wave-like properties. If we can use diffraction models to predict known lattice spacings, we can eliminate the possibility of maniacal channeling and strongly conclude that if one attempts to measure an electron’s wave properties, an electron behaves as a wave. In today’s experiment we are going to investigate electron waves by looking at their diffraction pattern after passing though a polycrystalline graphite sample supported by a fine mesh grid. The crystal structure for graphite is shown in the figure 1 below. Waves diffract from planes of atoms. As a result, most three-dimensional lattices serve as two- dimensional diffraction gratings. If the grating results from a single crystal, the diffraction pattern will be in the form of a two-dimensional array of “bright spots”. If the grating is formed by a polycrystal, i.e. a specimen containing many randomly oriented crystals the diffraction pattern should look like rings. If a cubic material, the diffraction pattern should be a single ring (only more if higher order diffraction fringes are observable). Figure 1: Schematic of the in-plane crystal structure of graphite.
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This note was uploaded on 11/01/2009 for the course SPEC TROSC difrractio taught by Professor Nidal during the Spring '09 term at Uni. Heidelberg.

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ElectronDiffraction - Electron Diffraction Equipment:...

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