Davisson–Germer experiment

The Davisson -Germer experiment was conducted in 1927 by Clinton Davisson and Lester Germer his former assistant at Bell Laboratories. Underscoring Louis de Broglie's hypothesis of matter waves. 1937 Davisson was awarded for his experiment with the Nobel Prize for Physics.

Attempt

The test consists of an electron source, a crystal and a Faraday cup, and was carried out in vacuum. Electrons, the speed of which can be regulated by the acceleration voltage to be scattered by the crystal at a scattering angle. In the original experiment, a polished nickel crystal was used. The electron beam is oriented perpendicular to the crystal surface. It was ensured that only elastically scattered electrons were detected. By using the Faraday cup, the intensity of the scattered electrons as a function of measured. The test result as described below was observed when it was heated by the infiltration of air into the test apparatus of the crystal to remove the resulting oxide, thereby monocrystalline structures formed on the crystal surface which was broader than the electron beam.

Observation

Classically, one would expect that the intensity of the electrons is the same for each scattering angle. Experimentally, however, showed that it depends on him, it results in an interference pattern. The angle at which the maxima occur which fulfill the Bragg equation, which was erected in 1912 by William Lawrence Bragg for the diffraction of X-rays by crystals. Under certain conditions, electrons thus behave like electromagnetic radiation.

Historical

In 1924, Louis de Broglie hypothesized that matter has properties similar to those of a wave. One of the conclusions is that there may be interference with the particles. Walter Elsasser suggested before 1925 to demonstrate the wave nature of slow electrons by scattering on single crystals. Neither the work of de Broglie still Alsatian proposal Davisson and Germer were announced at the beginning of their experiment. The wavelength of electrons is very small, so objects on which they can be bent, also have to be very small. Until the diffraction at a double slit, it would take almost 40 years: in 1959, succeeded Claus Jönsson at the University of Tübingen, a corresponding experiment.