1. Joachim Stöhr Stanford Synchrotron Radiation Laboratory X-Ray Absorption Spectroscopy http://www-ssrl.slac.stanford.edu/stohr J. Stöhr, NEXAFS SPECTROSCOPY, Springer Series in Surface Sciences 25, (Springer, Heidelberg, 1992). J. Stöhr and H. C. Siegmann MAGNETISM: FROM FUNDAMENTALS TO NANOSCALE DYNAMICS, Springer Series in Solid State Sciences 152, (Springer, Heidelberg, 2006)

2. Physical Processes

3. Fermi's Golden rule Kramers- Heisenberg relation Quantum Theoretical X-Ray Interactions with Matter: The Basic Processes

4. Tunable x- rays offer large interaction cross sections neutrons electrons optical light Photoemission

5. Thomson Cross section http://www-cxro.lbl.gov/index.php?content=/tools.html Kortright and Kim, Phys. Rev. B 62, 12216 (2000) Fe atom X-Ray Absorption and Scattering Cross Sections per Atom Experiment Fe metal f 1 and f 2 tabulated Henke-Gullikson factors

6. X-ray Absorption Spectra in a Nutshell tabulated Henke-Gullikson

7. Absolute absorption coefficients from experimental spectra (from Henke-Gullikson compilation)

8. Names: XAFS – NEXAFS –XANES - EXAFS Interference of outgoing photoelectron and scattered waves Nearest neighbor distances Number of neighbors or XANES

9. Tunable x-rays offer elemental specificity

10. Experimental Soft X-rayTechniques

11. Experimental X-Ray Absorption Techniques

12. X-Ray Absorption versus Photoemission

13. Electron Yield Sampling Depth

14. Surface sensitivity of total and Auger yield

15. total yield

17. Some Fundamental X-Ray Absorption Spectra -- soft x-rays --

18. NEXAFS spectra of polymers: building block picture

19. Chemical Sensitivity Core level shifts and Molecular orbital shifts

21. NEXAFS of Transition Metals Dipole selection rule 2p 3d - strong 2p 4s - weak Total intensity reflect number of empty holes Ebert et. al. Phys. Rev. B 53, 16067 (1996). “white lines”

23. Polarized X-Rays - Dichroism “dichroism” = pol. dep. absorption

24. Polarization definitions (high energy physics) Historical note: different “handedness” definitions in optics (space) versus high energy physics (time)

26. Polarized x-rays offer orientation sensitivity Antiferromagnetic order Orientational order Chirality Ferromagnetic order

27. X-Ray Natural Linear Dichroism

29. C. T. Chen et al. PRL 68, 2543 (1992) Linear Charge Dichroism in a d-electron system

30. J. Stöhr et al., Science 292, 2299 (2001)

31. X-Ray Magnetic Linear Dichroism

32. sum Magnetic field splits p-orbitals

33. XMLD – spectra below and above T N Lüning et al. Phys. Rev. B 67, 214433 (2003)

34. XMLD spectra of two oxides

35. XMLD effects especially strong in multiplet peaks (Ni 2+,d 8 ) (Ni 1+,d 9 )

36. X-ray Magnetic Circular Dichroism

37. Magnetic Circular Dichroism

38. Soft x-rays are best for magnetism

39. XMCD spectra of the pure ferromagnetic metals

40. The sum rules

42. =0 for x-rays DipoleChirality  k=k 0  /c X-ray Natural Circular Dichroism

43. Pasteur’s and Faraday’s experiments