X-Ray Emission Spectroscopy and Resonant Inelastic Soft X-ray Scattering Photons in and Photons out For Synchrotron Radiation 21/12 2011

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

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

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

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

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

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

Still going strong…

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

Experiment

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

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

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

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

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…

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)

’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, 193002 (2010)

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”

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)

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

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

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

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

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

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

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

VERITAS at MAX-IV Cartoon by project manager Marcus Agåker