LSF Scientific Highlights and News
Transition metals, characterized by their partially filled d-orbitals, provide the basis for many of the most relevant processes in chemistry, biology, and physics. Embedded as single atoms or in small clusters, they give rise to exceptional optical, chemical, and magnetic properties. So far, it has proven impossible to disentangle the complex network of excited quantum states, which greatly hinders predicting and controlling of material properties. We employed double-resonant four-wave mixing spectroscopy to quantitatively resolve the bright and perturbing dark quantum states of the neutral copper dimer.
Ultra-fast operando X-ray diffraction experiments reveal the temporal evolution of low and high temperature phases and the formation of residual stresses during laser 3D printing of a Ti-6Al-4V alloy. The profound influence of the length of the laser-scanning vector on the evolving microstructure is revealed and elucidated.
Christoph Bostedt, Head of the Laboratory for Femtochemistry, was named APS Felllow. He received his fellowship certificate at at the 50th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics (DAMOP) APS Meeting in Milwaukee.
In the week of April 1-5 PSI welcomes 20 PhD students and postdocs taking part in the European HERCULES 2019 school on Neutron and Synchrotron Radiation. They will attend lectures and perform two days of practical courses at several beam lines of the Swiss Light Source.
Light alkanes are abundantly available and cheap resources that are often burned at oil wells because of the missing infrastructure for valorization. Novel technologies are needed for their selective functionalization to use natural gas as an energy vector in the transition between the oil and the renewables era. Catalytic oxyhalogenation may unlock the transformation of cheap and abundant alkanes into commodities. When chlorine-based reactions are compared with bromine, improved selectivities above an iron catalyst arise from surface-confinement of the reaction mechanism in the case of chlorine as halogen.
To date the electrochemical activity of battery materials was always relying in the oxidation/reduction of cationic redox (change of oxidation state of transition metals generally). However, recently, it was established in new cathode materials (so call Li-rich cathode) that the oxygen from the crystal lattice might also play the role of anionic redox center leading to enhance then the specific charge of battery materials.
The high brilliance of new X-ray sources such as X-ray Free Electron Laser opens the way to non-linear spectroscopies. These techniques can probe ultrafast matter dynamics that would otherwise be inaccessible. One of these techniques, Transient Grating, involves the creation of a transient excitation grating by crossing X-ray beams on the sample. Scientists at PSI have realized a demonstration of such crossing by using an innovative approach well suited for the hard X-ray regime.
Structural selectivity of supported Pd nanoparticles for catalytic NH3 oxidation resolved using combined operando spectroscopy
The link between Pd nanoparticle structure and surface reactivity for NH3 abatement was found using operando X-ray absorption fine structure spectroscopy, diffuse reflectance infrared Fourier-transformed spectroscopy and on-line mass spectrometry.
A major milestone in the commissioning of SwissFEL has been reached: the first pump-probe experiments on proteins have been successfully carried out. Crystals of several retinal-binding proteins were delivered in a viscous jet system and a femtosecond laser was used to start the isomerization reaction. Microsecond to sub-picosecond snapshots were then collected, catching the retinal proteins shortly after isomerization of the chromophore.