The Röntgen Radiation and its application in studies of ... - Mansic

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When, through the occupation of the free orbital by an electron from the exterior orbits the ionized atom comes back to its normal state, a secondary X radiation is emitted, known as fluorescence radiation. The fluorescence radiation spectrum is a spectrum of lines that is characteristic for the material subjected to the radiation. From the equation it is obvious that the wavelength of the fluorescence radiation Has higher value, than that, of the incoming radiation. h ∆λ = ⋅ 2 m ⋅ c ( 1− cos θ ) The incoherent scattering of the X rays. The incoherent scattering (or Compton effect) was explained by A.H. Compton as an elastic collision between an X photon and free or lose tide electron. During the collision, some of energy of the incoming photon is passed to electron. After the collision, the energy of the photon is slightly smaller. In consequence, scattered radiation has a wavelength slightly bigger than that of the incoming radiation. The coherent scattering of the X rays. Also, the scattering of the X rays by electrons on an atom can take place coherently. According to J. J. Thomson’s theory of coherent scattering, electron is put in oscillating motion by incoming electromagnetic wave (the X radiation). In this forced oscillating movement, with its frequency equal to that of the electric field of the electromagnetic wave, electron is continuously accelerated or decelerated and as a result of that it emits an electromagnetic wave having a wavelength the same as incoming radiation. Although X rays are scattered by the electron in all directions, the intensity of the radiation according to J. J. Thomson’s equation, depends on the scattering angle: ⎛ I = I ⋅ ⎜ 0 ⎝ r 2 e ⋅ m 4 2 ⋅ c 4 ⎞ ⎛ 2 2 ⋅θ ⎞ ⎟ ⋅⎜1 + cos ⎟ ⎠ ⎝ 2 ⎠ In this equation, I0 represents the intensity of primary beam, I – the intensity of scattered radiation, 2θ – the scattering angle. ⎛ 2 2 ⋅θ ⎞ The factor ⎜1+ cos ⎟ ⎝ 2 ⎠ is called polarization factor due to the fact that crystallographic planes play role of polarizator for X-ray. 5. Basics of Crystallography A crystal consists of a periodic arrangement of the unit cell into a lattice. The unit cell can contain a single atom, ion or molecular in a fixed arrangement. Figure 6. : The structure of CsCl crystal Physics of Advanced Materials Winter School 2008 8
Crystal net is built from planes of atoms that are spaced at a distance d. Many atomic planes can be distinguished, however, each one with a different d-spacing. In the unit cell, a, b and c (length) and α, β and γ angles between a, b and c are lattice constant or parameters, which can be determined from X-ray diffraction measurement. 5.1. Crystal Systems and Space Lattices Depending on the atom arrangement in the lattice a given structure can be assigned to one of six crystal systems characterized by the ratios of the lattice parameters: a, b and c-and the three angles defined by those edges –α =
Page 1 and 2: The Röntgen Radiation and its appl
Page 3 and 4: The next improvement was introduced
Page 5 and 6: 2. The production of X-rays The X r
Page 7: Due to the fact that Kβ and Kα2 a
Page 11 and 12: Figure 10. A Modern Automated X-ray
Page 13 and 14: a) b) Intensity 20 40 60 80 100 120
Page 15 and 16: technique is used for determination
Page 17 and 18: In te ns it y Temperature 0 C 2θ F

The Röntgen Radiation and its application in studies of ... - Mansic

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