Davisson-Germer experiment

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The Davisson-Germer experiment was carried out in 1927 by Clinton Davisson and his then assistant Lester Germer at Bell Laboratories . They thus confirmed Louis de Broglie's hypothesis of matter waves . In 1937 Davisson was awarded the Nobel Prize in Physics for his experiment .

attempt

Setup of the experiment

The experiment consists of an electron source , a crystal and a Faraday beaker and was carried out in a vacuum. The electrons , the speed of which can be controlled via the acceleration voltage , are scattered on the crystal at a scattering angle . A polished nickel crystal was used in the original experiment. The electron beam is aligned perpendicular to the crystal surface. It was ensured that only elastically scattered electrons were detected. With the help of the Faraday cup, the intensity of the scattered electrons is measured as a function of . The test result described below was observed when, after air had penetrated the test device, the crystal was heated to remove the oxide formed and monocrystalline structures were formed on the crystal surface that were wider than the electron beam.

observation

Classically, one would expect the electron intensity to be the same at every scattering angle. Experimentally, however, it has been shown that it depends on him, resulting in an interference pattern . The angles at which the maxima result satisfy the Bragg equation , which was established in 1912 by William Lawrence Bragg for the diffraction of X-rays on crystals. Under certain conditions, electrons behave like electromagnetic radiation .

Historical

In 1924, Louis de Broglie hypothesized that matter has properties that correspond to those of a wave. One of the implications is that particles can interfere. In 1925, Walter Elsasser suggested that the wave properties of slow electrons should be demonstrated by scattering on single crystals. Davisson and Germer were not aware of either de Broglie's work or Alsace's suggestion when they began their experiment. The wavelength of electrons is very small, which is why objects on which they can be bent must also be very small. It was to be almost 40 years before the diffraction at the double slit : it was not until 1959 that Claus Jönsson at the University of Tübingen managed to conduct a corresponding experiment.

Individual evidence

  1. ↑ Davisson, C. and Germer, LH: Diffraction of Electrons by a Crystal of Nickel . In: Phys. Rev. Band 30 , 1927, pp. 705-740 .
  2. ↑ Information from the Nobel Foundation on the 1937 award ceremony for Clinton Joseph Davisson (English)
  3. ^ A b Paul Allen Tipler, Ralph A. Llewellyn: Modern Physics . Oldenbourg Verlag, November 2009, ISBN 978-3-486-58275-8 , p. 242– (accessed April 14, 2013).