Dr. Abdurahim Okhunov Associate Professor Department of Science in Engineering

particles should be able to behave like waves.

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• 2. Wave properties of microparticles:
• de Broglie Waves

• p = h/λ

• (4)

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• Diffraction of particles

• The diffraction of particles, scattering of microparticles (electrons, neutrons, atoms, etc.) by crystals or molecules of liquids and gases, in which additionally deflected beams of these particles arise from the initial particle beam of this type.
• The direction and intensity of such deflected beams depends from the building of scattering object.
• The Particle Diffraction can only be understood on the basis of quantum theory.
• Diffraction – is a wave phenomena, it is observed on the propagation of wave in difference nature: light diffraction of light, sound wave, wave on the surface of liquid and others.

• From the point of classical physics the diffraction during the particle scattering is impossible.
• The Quantum mechanics is eliminated the absolute boundary between the wave and particles.
• The basic principle of quantum mechanics, which describes the behavior of microobjects, occurs corpuscular-wave dualism, i.e. the dual nature of microparticles.
• Thus, the behavior of electrons in certain phenomena, for example, when observing their motion in a Wilson chamber or when measuring an electric charge in a photoelectric effect, can be described on the basis of ideas about particles. In others, especially in diffraction phenomena, only on the basis of the concept of waves.
• The idea of “waves of matter”, expressed by the French physicist L. de Broglie, was brilliantly confirmed in experiments on particle diffraction.

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• 3. Davisson and Jermer Experiment

• Nickel block had been heated up to remove oxide from surface.
• The experimental arrangement used by Davisson and Germer is schematically shown in this Figure 1.

• Figure 1
• Davisson and Gerner electron diffraction arrangement.

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• The first experiment on particle diffraction, which brilliantly confirmed the initial idea of quantum mechanics – wave–particle duality, was the experience of American physicists C. Davisson and L. Germer conducted in 1927 on electron diffraction on nickel single crystals:

• Experiments on particle diffraction
• and their quantum mechanical interpretation

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• Crystals have a high degree of ordering.
• The atoms in them are located in a three–dimensionally periodic crystal lattice, i.e. a spatial diffraction grating are formed for the corresponding wavelengths.

• Electron diffraction on nickel single crystals

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• (5)

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• Ni single crystal

• diffraction peaks

• electron beam

• in Davisson and Jermer Experiments on “reflection” of the electrons at certain angles of reflection, arose maxima from the surface of nickel crystal.

• A beam of electrons from a heated filament, accelerated through a potential

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• At higher accelerating electric voltages (tens of kV), the electrons acquire sufficient kinetic energy to penetrate thin films of matter (about 10–5 cm thick, that is, thousands of Å).
• Then, the so–called passing of fast electron diffraction arises, which was first studied on polycrystalline aluminum and gold films by the English scientist J. J. Thomson and the Soviet physicist P. S. Tartakovsky.

• Soon after this, the diffraction of atoms and even molecules was also observed!

• The electrons diffraction on the mica (слюде)

• The neutrons diffraction on the quartz

• This means that
• the wave properties are
• inherent in all particles
• of the microworld.

• In 1927 J.P. Tomson and P.C. Tartokpovsky obtained the picture of diffraction an electron beam passed through metal foil.

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• 4. The experiments of Thomson and Tartakovsky

• The particle diffraction, once played such a large role in establishing the dual nature of matter: wave – particle duality (and thereby serving as an experimental justification for quantum mechanics), has long been one of the main working methods for studying the structure of matter.

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• Two important modern methods for analyzing the atomic structure of matter are based on particle diffraction:
• – electron diffraction and neutron diffraction.

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