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by: sachinjadhav

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2 : X-Ray Diffraction Presented by- Mr. Sachin M. Jadhav M.Pharm-I (Pharmaceutics) SVERI’s College of Pharmacy, Pandharpur. 2
4 : CONTENTS What is light ? What are x-rays ? Why x-rays preferred ? How they are produced ? A) atomic level B) Instrumental level How target metal selected ? Which are useful radiations for analysis ? What is diffraction ? What is BRAGG’s equation ? What is a crystal ? 4
5 : CONTENTS X-ray diffraction at crystal structure Instrumentation for x-ray diffraction Detectors Different patterns of solid ,liquid & gases Methods of crystal structure determination Various x-ray diffraction patterns with example Fourier transformations Phase problem Phasing methods Ring patterns & sizes achievements 5
6 : Theory of light 6
7 : X-ray -0.01nm-10nm Visible light- 400-800 nm 7
8 : Why do we use X-rays? Visible light- 400-800 nm atomic distances- ~ 1.5 Å X-ray - 0.01nm-10nm (0.1 Å - 100Å) Used x-ray range- 0.7Å - 3Å 8
9 : Dimensions of life 9 X-rays
10 : Theory of x-ray at atomic level Inner orbit Outer orbit 10
11 : Instrumentation for x-ray tube 11
12 : X-ray production at instrumental level 12
13 : Coolidge tube  Coolidge tube was invented in the GE company laboratories by W.D. Coolidge. It had a hot cathode in which electrons were liberated through the process of thermionic emission. It also had a metal target, using high atomic number metallic target increased efficiency of x-ray production. 13
14 : Target metal selection 14
15 : Intensity Wavelength (?) Mo Target impacted by electrons accelerated by a 35 kV potential 0.2 0.6 1.0 1.4 White radiation Characteristic radiation ? due to energy transitions in the atom K? K? 15
16 : Reflection vs Diffraction 16
17 : BRAGG’s EQUATION Bragg’s equation is a negative law ? If Bragg’s eq. is NOT satisfied ? NO reflection can occur ? If Bragg’s eq. is satisfied ? reflection MAY occur 1915 W.H. Bragg & W.L. Bragg : (Nobel Prize Physics) 17
18 : BRAGG’s EQUATION d ? ? ? ? dSin? The path difference between ray 1 and ray 2 = 2d Sin? For constructive interference: n? = 2d Sin? Ray 1 Ray 2 ? Deviation = 2? 18
19 : Crystal structure 19
20 : A beam of X-rays directed at a crystal interacts with the electrons of the atoms in the crystal X-Rays and become secondary sources of EM radiation The secondary radiation is in all directions The waves emitted by the electrons have the same frequency as the incoming X-rays ? coherent Incoming X-rays Secondary emission 20
21 : Sets Electron cloud into oscillation Sets nucleus (with protons) into oscillation Small effect ? neglected The electrons oscillate under the influence of the incoming X-Rays and become secondary sources of EM radiation 21
22 : Oscillating charge re-radiates ? In phase with the incoming x-rays The emission will undergo constructive or destructive interference with waves scattered from other atoms 22
23 : Instrumentation for x-ray diffraction 23
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26 : Detectors Scintillators Some materials such as sodium iodide (NaI) can "convert" an X-ray photon to a visible photon; an electronic detector can be built by adding a photomultiplier. These detectors are called "scintillators", filmscreens or "scintillation counters". Geiger-Muller counter most common detection methods were based on the  ionization of gases, as in the : a sealed volume, usually a cylinder, with a mica, polymer or thin metal window contains a gas,acylindrical cathode and a wire anode a high voltage is applied between the cathode and the anode. 26
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28 :  It is the new generation of X ray diffraction products from Bruker AXS. The system includes two independent X-ray safety circuits All components like tube housing, X-ray optics, and detectors are mounted on high-precision tracks and can be readily exchanged with reproducible positioning and freely moved along the tracks. The  D8 ADVANCE goniometer is equipped with stepper motors controlled by optical encoders. The Dynamic Scintillation Detector with low background, large dynamic range, and a long life time D8 ADVANCE 28
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