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Single scattering: when an electron is scattered just once. Plural scattering: when electron(s) scatter several times. Multiple scattering: when electron(s) scatter many times over. The likelihood of an electron scattering and the degree of the scattering is a function of the specimen thickness and the mean free path. [6]
Davisson began work in 1921 to study electron bombardment and secondary electron emissions. A series of experiments continued through 1925. Prior to 1923, Davisson had been working with Charles H. Kunsman on detecting the effects of electron bombardment on tungsten when they noticed that 1% of the electrons bounced straight back to the electron gun in elastic scattering. This sm
Close to an aperture or atoms, often called the "sample", the electron wave would be described in terms of near field or Fresnel diffraction. [12]: Chpt 7-8 This has relevance for imaging within electron microscopes, [1]: Chpt 3 [2]: Chpt 3-4 whereas electron diffraction patterns are measured far from the sample, which is described as far-field or Fraunhofer diffraction. [12]:
The relation between scattering and correlation functions is the LSZ-theorem: The scattering amplitude for n particles to go to m particles in a scattering event is the given by the sum of the Feynman diagrams that go into the correlation function for n + m field insertions, leaving out the propagators for the external legs.
For calcium (Z=20), Compton scattering starts to dominate at hυ=0.08 MeV and ceases at 12 MeV. [69] When photon energies are as high as the electron rest energy of 511 keV, yet another process, Compton scattering, may occur. Above twice this energy, at 1.022 MeV, pair production is also more likely. [70]
Though discovered in 1927, low-energy electron diffraction did not become a popular tool for surface analysis until the early 1960s. The main reasons were that monitoring directions and intensities of diffracted beams was a difficult experimental process due to inadequate vacuum techniques and slow detection methods such as a Faraday cup.
In many areas of science, Bragg's law, Wulff–Bragg's condition, or Laue–Bragg interference are a special case of Laue diffraction, giving the angles for coherent scattering of waves from a large crystal lattice. It describes how the superposition of wave fronts scattered by lattice planes leads to a strict relation between the wavelength ...
However, Klein's result showed that if the potential is at least of the order of the electron mass (where V is the electric potential, e is the elementary charge, m is the electron mass and c is the speed of light), the barrier is nearly transparent. Moreover, as the potential approaches infinity, the reflection diminishes and the electron is ...