Lect13_notes

33 cbems 164 xrd sem microanalysis lecture 13 34 a

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Unformatted text preview: icroanalysis: Lecture 13 ! 32 ZAF factors in Microanalysis! Atomic Number Effect: X-ray Absorption Effect: Fluorescence Effect: Z – Atomic Number Effect! •  Backscattering, R –  Some electrons are backscattered and leave sample without exciting an x-ray •  No energy loss therefore no x-ray •  BS electron yield from a Au:1 Al alloy will be dominated by the Au and this must be accounted for if a pure Al standard is used for Al analysis. •  Can model with Monte Carlo simulations •  Energy Loss, S –  Rate of energy loss due to inelastic scattering depends on Z CBEMS 164 – XRD, SEM & Microanalysis: Lecture 13 ! 33 CBEMS 164 – XRD, SEM & Microanalysis: Lecture 13 ! 34 A- X-Ray Absorption Effect! •  Once generated, x-rays have to traverse sample until they exit the top surface –  Some are absorbed, possibly ejecting inner shell electrons from their sites - inner shell ionization –  Higher keV results in a longer traverse path I/I0 = exp[-(µ/)(t)] µ/ is mass absorption coefficient F - Flourescence! •  Ionizations of inner atomic shells can result...
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This note was uploaded on 01/16/2014 for the course CBEMS 164 taught by Professor Porter,j during the Fall '08 term at UC Irvine.

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