Ken Finkelstein Materials Science Professor Robinson's class

Ken Finkelstein Materials Science Professor Robinson's...

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MSE 2060 - Atomic and Molecular Structure of Matter Professor R. Robinson contributed by K.D. Finkelstein - CHESS Wilson Lab, Cornell Univ. Outline: Introduction (how x-rays interact with materials) everal techniques based on x y absorption Several techniques based on x-ray absorption EXAFS, XANES, XES An art full application Most slides are borrowed from talks by colleagues: Yves Joly, Lois Pollack, Jennifer Mass, Serena deBeer George, & others
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Photon absorbed, “core hole” created, lectron “ ills hole” electron fills hole , new photon emitted. electrons oscillate, at ω , in E-field of photon System exchanges energy with incident photon Y. Joly (CNRS) 2009
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Y. Joly (CNRS) 2009
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Absorption ~ 1 – Transmission ~ 1 – I/I 0 = 1 – e -μ(E)D J.-L. Hazemann, O. Proux et al. CRG FAME, ESRF Y. Joly (CNRS) 2009
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For any chemical element there is a set of absorption edges KL 2 M 2 13.6 Some edges (eV) Fermi M 5 H 3.6 C 284.2 Fe 7112 720 52.7 n = 3 = 1 = 2 M 2 M 3 M 4 Ag 25514 3524 604 U 115606 20948 5182 n = 2 = 0 = 1 L 2 L 3 M 1 spin-orbit spreads level between 2 = 0 K L 1 Deeper is the edge n = 1 = 0 6 Shorter is the time life Broader is the edge Y. Joly (CNRS) 2009
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X-ray absorption - followed by emission Increasing electron binding energy Empty states illed states 0 eV Filled states Incident x-ray Fluorescence x-ray (signal of absorption) Inner core state
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Extended x-ray absorption fine structure - EXAFS λ k = wave vector of radiated photoelectron = 2 π / λ = [2m/ ħ
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Ken Finkelstein Materials Science Professor Robinson's...

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