Electron Diffraction Experiments

Lester Germer (right) with Clinton Joseph Davi...Image via WikipediaTwo seminal experiments were reported in 1925. One of these, commonly referred to as the Davisson–Germer experiment, was performed in the United States. The other was performed by G. P. Thomson and his coworkers in Great Britain. These experiments are complementary to the photoelectric effect because, while the explanation of the photoelectric effect relied on the particle nature of light, the explanation of these results relied on the wave nature of particles (electrons). This made clear that the same wave–particle duality associated with photons exists for material particles. Just how particles behave as waves is the subject of this book and, indeed, quantum physics. More about that later in this chapter.
    Davisson and Germer were studying electron scattering from metallic surfaces when an experimental
accident forced them to subject a nickel surface to a high temperature. The effect was to crystallize the nickel and make it, in effect, a diffraction grating for electrons. The data were explainable as a diffraction pattern. That is, the electrons were interfering with each other in the same way that light waves were known to interfere to produce familiar diffraction patterns. This experiment was performed after Louis de Broglie’s hypothesis (see below) that ascribed wave properties to matter. The explanation of the data was consistent with de Broglie’s hypothesis. Thomson’s experiments were also consistent with de Broglie’s hypothesis. They were similar in nature to the Davisson–Germer experiment, but Thomson used thin metal foils as the “diffraction grating.”
In 1937 Clinton Joseph Davisson and George Paget Thomson shared the Nobel Prize in Physics “for their experimental discovery of the diffraction of electrons by crystals.” Interestingly, George Thomson was the son of yet another Nobel laureate, Joseph John Thomson, who was awarded the Nobel Prize in 1906 “in recognition of the great merits of his theoretical and experimental investigations on the conduction
of electricity by gases”. In summary, while the wave–particle duality was hard to understand for photons,
it was virtually incomprehensible for material particles. The question to be answered was: what is it that is doing the waving? This is the subject of this book.

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reference : C.E. Burkhardt, J.J. Leventhal, Foundations of Quantum Physics, 1
DOI: 10.1007/978-0-387-77652-1 1, C Springer Science+Business Media, LLC 2008


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