Scientific Highlights
Exciting Heavy Metal
Photocatalysts play an important role in a broad range of applications, from photochemical conversion of light energy into chemical energy through to initiating novel chemical reactions. One family of compounds that has attracted much attention is the dinuclear d8-d8 platinum, rhodium and iridium complexes that have a highly reactive electronic excited state.
Femtosecond molecular spin crossover
X-ray absorption spectroscopy is a powerful probe of molecular structure, but it has previously been too slow to track the earliest dynamics after photoexcitation. We investigated the ultrafast formation of the lowest quintet state of aqueous iron(II)tris(bipyridine) upon excitation of the singlet metal-to-ligand-charge-transfer (1MLCT) state by femtosecond optical pump/x-ray probe techniques based on x-ray absorption near-edge structure (XANES).
Building blocks of an artificial kagome spin ice: Photoemission electron microscopy of arrays of ferromagnetic islands
Arrays of dipolar coupled ferromagnetic islands arranged in specific geometries provide ideal systems to
directly study frustration. We have examined with photoemission electron microscopy the magnetic configurations
in three basic building blocks of an artificial kagome spin ice consisting of one, two, and three rings.
The kagome spin ice arrangement is particularly interesting because it is highly frustrated and the three
Super-Resolution X-ray Microscopy unveils the buried secrets of the nanoworld
A novel super-resolution X-ray microscope developed by a team of researchers from the Paul Scherrer Institut (PSI) and EPFL in Switzerland combines the high penetration power of x-rays with high spatial resolution, making it possible for the first time to shed light on the detailed interior composition of semiconductor devices and cellular structures.
The first super-resolution images from this novel microscope will be published online July 18, 2008 in the journal Science.
Nanoscale depth resolution of lattice dynamics
We employ grazing-incidence femtosecond x-ray diffraction to characterize the coherent, femtosecond laser-induced lattice motion of a bismuth crystal as a function of depth from the surface with a temporal resolution of ~200 fs. The data show direct consequences on the lattice motion from carrier diffusion and electron-hole interaction, allowing us to estimate the effective diffusion rate for the highly excited carriers and the electron-hole interaction time.
Coherent Diffraction Imaging Using Phase Front Modifications
We introduce a coherent diffractive imaging technique that utilizes multiple exposures with modifications to the phase profile of the transmitted wave front to compensate for the missing phase information.
X-ray dark-field imaging using a grating interferometer
A type of X-ray imaging that shows detail otherwise lost, and which is compatible with conventional radiography instrumentation is now feasible, reports a study published online in Nature Materials. This technique offers unprecedented resolution for several applications, including medical imaging, security screening and industrial non-destructive testing.
Stable Source of Femtosecond X-Ray Pulses at SLS – Pushing atoms on a swing
The typical time scale of atomic motion during fundamental physical processes such as phase transitions in solids or molecular dynamics in chemical reactions ranges from ten to hundreds of femtoseconds. The direct observation of these processes on an atomic length scale therefore requires utrashort light pulses at wavelengths capable of resolving the underlying atomic structures.
Pushing atoms on a swing
The typical time scale of atomic motion during fundamental physical processes such as phase transitions in solids or molecular dynamics in chemical reactions ranges from ten to hundreds of femtoseconds. The direct observation of these processes on an atomic length scale therefore requires utrashort light pulses at wavelengths capable of resolving the underlying atomic structures.
Vibrational spectra of adsorbates from DFT
The hydrolysis of isocyanic acid was studied experimentally and theoretically and a reaction mechanism on different catalysts was established. The decreasing NOx emission limits for diesel vehicles impel the further development of the existing NOx deactivation technologies, particularly the selective catalytic reduction (SCR) of nitrogen oxides with urea. In the urea-SCR process, urea is injected into the hot exhaust gas, where it thermally decomposes into isocyanic acid (HNCO) and ammonia.