Filtering of X-ray Choose for the filter an element whose k absorption edge is just to the short-wavelength side of the Ka line of the target materia a common example is absorption the use of nickel to cut edge of down the KB peak in the Ea Cu K 4881 copper x-ray spectrum. n540 The thickness of the filter to achieve the desired <2 intensity ratio of the peaks can be calculated 12 18 with the absorption equation shown in the No filter Ni filter last section Comparison of the spectra of cu radiation(a before and(b) after passage through a Ni filter. The e e dashed line is the mass absorption coefficient of n
▪ A common example is the use of nickel to cut down the K peak in the copper x-ray spectrum. ▪ The thickness of the filter to achieve the desired intensity ratio of the peaks can be calculated with the absorption equation shown in the last section. Filtering of X-ray x x I I e I e − − = 0 = 0 Comparison of the spectra of Cu radiation (a) before and (b) after passage through a Ni filter. The dashed line is the mass absorption coefficient of Ni. No filter Ni filter K absorption edge of Ni 1.4881Å Choose for the filter an element whose K absorption edge is just to the short-wavelength side of the K line of the target material. Cu K 1.5405Å
What Is diffraction? A wave interacts with A single particle The particle scatters the incident beam uniformly in all directions Particle A crystalline material The scattered beam may add together in a few directions and reinforce each other to gIve diffracted beams Cryst http://www.matter.org.uk/diffraction/introduction/what_is_diffraction.htm
What Is Diffraction? A wave interacts with A single particle A crystalline material The particle scatters the incident beam uniformly in all directions. The scattered beam may add together in a few directions and reinforce each other to give diffracted beams. http://www.matter.org.uk/diffraction/introduction/what_is_diffraction.htm
What is X-ray Diffraction? The atomic planes of a crystal cause an incident beam of x-rays(if wavelength is approximately the magnitude of the interatomic distance) to interfere with one another as they leave the crystal The phenomenon is called x-ray diffraction Bragg's Law: n2= 2dsin(0) Diffraction 久~d pattern Diffracted beam recorded 20B Incident beam atomic plane 2 X-ray of 2 0d 工 Transmitted beam Crystalline material http://www.youtube.com/watch?v=1fwm1of5e6otow1:17diffraction&interference
What is X-ray Diffraction? The atomic planes of a crystal cause an incident beam of x-rays (if wavelength is approximately the magnitude of the interatomic distance) to interfere with one another as they leave the crystal. The phenomenon is called x-ray diffraction. atomic plane X-ray of d Bragg’s Law: n= 2dsin() B ~ d 2B I http://www.youtube.com/watch?v=1FwM1oF5e6o to~1:17 diffraction & interference
Constructive and destructive Interference of waves Constructive interference occurs only when the path difference of the scattered wave from consecutive layers of atoms is a multiple of the wavelength of the x-ray. Constructive Interference Destructive Interference Direction DD=Propagation Direction A= Amplitude Wavelength A/2 Ax+Aw,=A A= Amplitude (Resultant Waves in Phase Path Differnce o (Resultant) C=Vibration 4 Direction Wavelength C=Vibration Direction Constructive Interference Destructive Interference In phase Out phase http://www.youtube.com/watch?v=ksc_7xbng8w http://micro.magnetfsuedu/primer/java/interference/waveinteractions/index.html
Constructive and Destructive Interference of Waves Constructive Interference Destructive Interference In Phase Out Phase Constructive interference occurs only when the path difference of the scattered wave from consecutive layers of atoms is a multiple of the wavelength of the x-ray. /2 http://www.youtube.com/watch?v=kSc_7XBng8w http://micro.magnet.fsu.edu/primer/java/interference/waveinteractions/index.html
http://www.eserc.stonybrookedu/projectava/bragg/index.html Bragg's Law and X-ray Diffraction How waves reveal the atomic structure of crystals n2= 2dsin (0) n-Integer Diffraction occurs only when Bragg's Law is satisfied Condition for constructive interference(X-rays 1& 2) from planes with spacing d Incident X-ray1 detail Scattered beam X-ray2 入=3A 0=309 Atomic d=3A plane 20-diffraction angle Atomic planes Lambda Distance Theta 3.0 3.0 300 http://www.youtube.com/watch?v=ufdw0-kghmiat3:00-6:00
Bragg’s Law and X-ray Diffraction How waves reveal the atomic structure of crystals n = 2dsin() Atomic plane d=3 Å =3Å =30o n-integer X-ray1 X-ray2 2-diffraction angle Diffraction occurs only when Bragg’s Law is satisfied Condition for constructive interference (X-rays 1 & 2) from planes with spacing d http://www.youtube.com/watch?v=UfDW0-kghmI at~3:00-6:00 http://www.eserc.stonybrook.edu/ProjectJava/Bragg/index.html