1. X-Ray Emission Spectroscopy and Resonant Inelastic Soft X-ray Scattering Photons in and Photons out
For Synchrotron Radiation 21/

2. Outline General Introduction Local Partial Density of State
Site Selectivity
Typical attenuation length: 1000Å
Instrumentation
Soft X-ray spectrometers: Resolution, resolution, resolution and the new PGS
Synchrotron radiation: Brilliance, brilliance, brilliance and MAX-IV
RIXS; Resonant Inelastic Soft X-ray Scattering
Always a one-step process
Energy conservation
Momentum conservation
Symmetry selectivity
Dynamics
Interference and vibronic coupling
Core-hole clock
Applications
Complex Systems

3. X-ray emission: Characteristic radiation?
H. G. J. Moseley, M. A. Phil. Mag. (1913), p. 1024

4. Yes, but also uncharacteristic Valence electronic struture
Phys. Rev. 45, 370 (1935)

5. Local Partial Density of States
Core levels are atomic-like:
Local Properties
Dipole Selection rules are valid:
Symmetry Selectivity
Valence Band
Local
Si (s+d)
Si 2p
Local
C p
C 1s
Local Partial Density of States

6. Rapid development at new synchrotron radiation: Notoriously low count rates
Conduction
Intermediate
Valence
Core
0.1%
Final
Ground

7. Rowland spectrometer Source Detector Grating
Combining the focussing properties of a sphere with the dispersive properties of a grating

8. Still going strong…

9. New Concepts for efficiency and resolution
PGS:
Plane grating spectrometer
Two parabolic mirrors and a plane grating
FTS:
Fourier Transform Spectrometer
Wavefront Beamsplitters and mirrors in grazing incidence

10. Experiment

11. X-ray scattering; always a one-step process
Core Excited
Emission:
Absorption:
Valence Excited
Ground State

12. Linear approximation
M. Blume, J. Appl. Phys. 57, 3615 (-85): This equation ’accounts for
most scattering phenomena to the order of ’

13. Helium Doubly excited states 2l’n’l’’ Singly excited states 1snl
’One can get X-ray emission from everything except hydrogen and helium’
Distinguished Professor
Helium
Doubly excited states
2l’n’l’’
Singly excited states
1snl
Ground
1s2

14. Autoionizing resonances?
Schulz et al., PRL 1996
2l’n’l’’
1snl
1s + e
1s2
Autoionizing resonances?

15. Symmetry resolution in RIXS
Strict dipole selection rules:
J. Söderström et al., PRA 2008
Influence of s-o coupling and external fields, two-color experiments, PGS measurements…

16. The oxygen molecule ’ Where is the core hole?
’A core hole is localized at one atomic site’
Distinguished Professor
The oxygen molecule
3su
1pg
1pu
Right?
Left?
Both? O
Where is the core hole? ’
3sg
2su
2sg
1su
1sg
Strict dipole selection rules apply:
GeradeUngeradeGerade
Inversion symmetry is not broken
P. Glans, et al. PRL 76, 2488 (-96)

17. ’The core-hole lifetime width will always be limiting the information you can get out of RIXS spectra.’
Distinguished Professor
Hennies, et al. PRL. 104, (2010)

18. Controlling the nuclear motion
Potential surface and lifetime of the core excited state.
meV
4.2 fs Å
2.5 fs
1.5 fs
Scattering Duration Time
Concept developed by Faris Gel’mukhanov and Hans Ågren
0.88 fs
Constant-G approximation ”valid”
Constant-fluorescence-yield approximation ”valid”

19. O O O O Carbon Dioxide Scattering duration time!
Vibrations break the symmetry
2. But not if the energy is detuned O O O O
Scattering duration time!
P. Skytt, et al., PRL 77, 5035 (-96)

20. The Ultrafast Core-hole Clock
4d4f resonance in LaF3
Scattering:
Gives narrow peaks.
intensity indicates
that the 4f electron escapes during the
process:

21. Momentum Conservation
’But you can never do band mapping with X-ray emisson because the core hole destroys the translational symmetry.’
Distinguished Professor
Momentum Conservation
S. Eisebitt et al., 1998

22. Silicon Carbide again
J. Lüning et al., PRB56 -97

23. Correlated Materials Spin flips are forbidden in dipole transitions
Distinguished Professor
Correlated Materials

25. Site Selectivity in Complex Systems
’This gives me a headache’
Distinguished Professor
Site Selectivity in Complex Systems

26. Looking Through Windows
Several 1000 Ångström
-gases
-liquids
-gas/liquid/solid interfaces

28. Many applications of liquid studies
Biology, Pharmaceutics, Drug solubility
Electrochemistry, battery technology, corrosion
Environmental Science, etc...

29. VERITAS at MAX-IV
Cartoon by project manager Marcus Agåker