Special+Topics

=Special Topics=

//X-rays Radiation﻿//
====//X-rays are high energy electromagnetic radiation with atomic level wavelengths. For XRD, x-rays in the range of 0.5-2.5// Å are used which is adequate resolution for determining crystal structure arrangements. X-rays are produced when any electrically charged particle with sufficient kinetic energy strikes a target, thereby converting its energy into radiation. X-ray tubes normally use accelerating electrons across a cathode and anode plates and accelerating voltages around 35kV. Most of the energy of the electron striking the anode is converted to heat and about 1% is converted to x-rays. ====

Characteristic Spectrum
==== The x-rays produced form a characteristic spectrum unique to the target material as well as continuous radiation at lower kV ratings. The characteristic spectrum contain sharp peaks unique to the target material. The highest intensity peaks important for x-ray diffraction are known as K α peaks and appear in the characteristic spectrum when the //K critical excitation voltage// is exceed. Upon closer inspection the K peaks resolve into three different peaks and are labelled K α1, K α2, K β respectively. For a molybdenum target the peaks are at wavelengths 0.709 Å, 0.714 Å and 0.632 Å respectively. ====

x-rays Interaction.
==== When x-rays interact with matter they are both transmitted and absorbed. If we envision a simple Bohr model of the atom with shells labeled K,L, and M respectively. wh K,L,M where K,L, and M refer to orbital shells. The K shell is the innermost orbital level of the target material's atom and correlates to the 1s orbital. If an x-ray collides with an electron in this orbital it radiates its energy as x-rays and is replaced with an electron from a higher energy state, most likely the L or 2s orbital. However, the electron can come from any higher energy level.The electron that loses energy to place the 1s electron gives off energy characteristic of K radiation. Values for K,L,M values are tabulated for each element. ====

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