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Unformatted text preview: I n tens i ty Facto rs fo r X-Ray D i f f r act ion
• • nλ=2dsinθ • Each peak represents where a diffracting plane exists in the crystal • λ is fixed by the source (monochromatic) • Identifying the different values of d can give you more information about the
c rystal planes
o • Lattice info Basis info is inherent in the intensity of the peaks – tells you what is at each
l attice point • Intensity Factors
o Absorption factor o Multiplicity factor o Temperature factor o Lorenz polarization factor (geometric) o Structure factor • Absorption factor
o X-rays will be absorbed at a certain rate by the material o Remember from transmission: I= I0e-μx o In case of diffraction, geometry is different (from reflection) o o The x-rays are absorbed when going in and going out again o No specific orientation is implied between crystal grains so the only
grains that diffract are those in the right orientation o dID=a*b*l*dx*I0*e-μ(AB+BC) o Sliver: ldx – smallest amount of volume with smallest step o a = volume fraction of grains in right orientation o b = fraction of incident light that is diffracted by the unit volume (ldx) o l= 1sinγ, AB= xsinγ, BC= xsinβ o For x-ray diffraction, γ=β o ID= 0∞dID= I0-absinθsinθ*2μe-2μxsinθ= I0ab2μ o Diffracted intensity is not dependent on θ at all, so going over range of θ
doesn’t change it o
• Absorption factor affects all intensities equally Multiplicity Factor o
o Related to the number of planes in a family of planes- ...
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- Spring '09