Review: X-ray scattering methods with synchrotron radiation
Resonant X-ray excitation (purple) core excites the oxygen atom within a H2O molecule. This causes ultrafast proton dynamics. The electronic ground state potential surface (bottom) and the bond dynamics is captured by distinct spectral features in resonant inelastic X-ray scattering (right).
© Martin Künsting /HZB
Synchrotron light sources provide brilliant light with a focus on the X-ray region and have enormously expanded the possibilities for characterising materials. In the Reviews of Modern Physics, an international team now gives an overview of elastic and inelastic X-ray scattering processes, explains the theoretical background and sheds light on what insights these methods provide in physics, chemistry as well as bio- and energy related themes.
"X-ray scattering can be used to investigate and resolve a wide variety of issues from the properties and excitations of fuctional solids, to homogeneous and heterogeneous chemical processes and reactions or even the proton pathway during the splitting of water," explains Prof. Dr. Alexander Föhlisch, who heads the Institute Methods and Instrumentation for Research with Synchrotron Radiation at HZB.
The article gives an overview of experimental and theoretical results in the field of resonant scattering of tunable soft and hard X-rays. The focus is on resonant inelastic X-ray scattering (RIXS) and resonant Auger scattering (RAS). In the review, the authors outline the most important achievements from the last two decades at Synchrotrons up to the latest advances in time-resolved studies with X-ray free-electron lasers.
- BESSY II: How intrinsic oxygen shortens the lifespan of solid-state batteriesAlthough solid-state batteries (SSBs) demonstrate high performance and are intrinsically safe, their capacity currently declines rapidly. A team from the TU Wien, Humboldt-University Berlin and HZB has now analysed a TiS₂|Li₃YCl₆ solid-state half-cell in operando at BESSY II using a special sample environment that allows for non-destructive investigation under real operating conditions. Data obtained by combination of soft and hard X-ray photoelectron spectroscopy (XPS and HAXPES) revealed a new degradation mechanism that had not previously been identified in solid-state batteries. They have gained some surprising insights, particularly regarding the harmful role played by intrinsic oxygen. This study provides valuable information for improving design and handling of such batteries.
- Spintronics at BESSY II: Real-time analysis of magnetic bilayer systemsSpintronic devices enable data processing with significantly lower energy consumption. They are based on the interaction between ferromagnetic and antiferromagnetic layers. Now, a team from Freie Universität Berlin, HZB and Uppsala University has succeeded in tracking, for each layer separately, how the magnetic order changes after a short laser pulse has excited the system. They were also able to identify the main cause of the loss of antiferromagnetic order in the oxide layer: the excitation is transported from the hot electrons in the ferromagnetic metal to the spins in the antiferromagnet.
- Electrocatalysts: New model for charge separation at the solid-liquid interfaceHydrogen is at the heart of the transition to carbon neutrality, as both an energy carrier and a reagent for green chemistry. However, large-scale production of hydrogen via electrolysis, as well as the production of many other chemical products, requires significantly cheaper and more efficient catalysts. A precise understanding of the electrochemical processes that take place at the interface between the solid catalyst and the liquid medium is highly useful for developing better electrocatalysts. In the journal Nature Communications, an European team has now presented a powerful model that determines charge separation at the interface, the formation of the electric double layer and local electric potential variations, and the resulting influence on the catalytic activity.