Tracking attosecond wave packets with extreme ultraviolet pulses

The fastest dynamical process in atoms, molecules and complexes is the electronic motion. It occurs on time scales reaching down to the attosecond regime (1 as = 10-18 s).  The advent of novel light sources, providing extreme ultraviolet (XUV) or even X-ray pulses with as pulse duration paves the way to study these dynamics in real-time. Therefore, researchers around the world are currently developing new spectroscopic techniques using pulses of XUV or X-ray radiation.

An international research collaboration from Germany, Italy, Sweden, Switzerland, Denmark and the local team at the FERMI free-electron laser, has succeeded in observing the ultrafast electronic wave-packet evolution induced by the coherent excitation of an electron out of an inner shell in argon atoms. The measured quantum interference pattern exhibits oscillations that have a period of only ≈ 150 as. In order to achieve this, the collaboration extended a spectroscopy technique known from the visible spectral range – coherent wave-packet interferometry – to the XUV regime. This required a so far unprecedented level of control over the phase and timing properties of free-electron laser pulse pairs, which was achieved by exploiting the coherence of the high-gain harmonic generation process at FERMI. This novel spectroscopy technique will provide substantial insights and real-time information about intra and inter particle decay mechanisms in the XUV range.

Read more on the Elettra website

Image: Artistic rendering of the electronic motion in the electronic shell of an atom, induced and probed by a double pulse sequence.

Single atoms can make more efficient catalysts

Detailed observations of iridium atoms at work could help make catalysts that drive chemical reactions smaller, cheaper and more efficient.

Catalysts are chemical matchmakers: They bring other chemicals close together, increasing the chance that they’ll react with each other and produce something people want, like fuel or fertilizer.

Since some of the best catalyst materials are also quite expensive, like the platinum in a car’s catalytic converter, scientists have been looking for ways to shrink the amount they have to use.

Now scientists have their first direct, detailed look at how a single atom catalyzes a chemical reaction. The reaction is the same one that strips poisonous carbon monoxide out of car exhaust, and individual atoms of iridium did the job up to 25 times more efficiently than the iridium nanoparticles containing 50 to 100 atoms that are used today.

>Read more on the SSRL at SLAC website

Image: Scientists used a combination of four techniques, represented here by four incoming beams, to reveal in unprecedented detail how a single atom of iridium catalyzes a chemical reaction.
Credit: Greg Stewart/SLAC National Accelerator Laboratory

Funds for the latest generation of electron cryomicroscopy

The Polish Ministry of Science and Higher Education handed over to SOLARIS the official decision to establish the National Cryo-EM Centre at the Polish partner facility, granting the requested financial support.

The successful application is the result of an agreement and cooperation of 17 leading scientific institutions in Poland in the area of structural biology. This very unique nation-wide consortium, led by Dr. Sebastian Glatt (the Malopolska Centre of Biotechnology, Jagiellonian University, Kraków) and Dr. hab. Marcin Nowotny (the International Institute of Molecular and Cell Biology, Warsaw), was not only key to bring this breakthrough research technique to Poland, but also exemplifies how scientists from around the country are able to work efficiently together for a greater common goal. This state-of-the-art microscope will allow its users to follow the progress of other international research centres and will transfer Polish and international scientists into the first class of structural biology.

The advances made in cryo-EM have revolutionized the field of structural biology over the last decade. The increased recognition of this technology has also culminated in the Chemistry Nobel Prize being awarded to its creators in 2017. The development of this technique has opened up new research horizons, which resulted in a long list of groundbreaking studies published in the most prestigious scientific journals. Foremost, the anticipated results are extremely relevant for a better understanding of the function of the human body, of the formation of human diseases and of processes like aging, and can lead to the development of new effective therapies. Structural biology has already contributed to a huge progress in the treatment of various human diseases, including cancer, Alzheimer’s disease and obesity. Last but not least, the presence of a high-end cryo-electron microscope at SOLARIS means that Krakow will attract national and international structural biologists.

>Read more on the SOLARIS website

Image: The image of mimivirus made with the use of a cryo-electron microscope.
Credit: Xiao C, Kuznetsov YG, Sun S, Hafenstein SL, Kostyuchenko VA, et al. (2009) [CC BY 2.5]

The microstructure of a parrotfish tooth contributes to its toughness

During a 2012 visit to the Great Barrier Reef off the coast of Australia, ALS staff scientist Matthew Marcus became intrigued with parrotfish. “I was reminded that this is a fish that crunches up coral all day and is responsible for much of the white sand on beaches,” Marcus said. “But how can this fish eat coral and not lose its teeth?” So Marcus teamed up with Pupa Gilbert, a biophysicist at the University of Wisconsin–Madison, and an international team of researchers she assembled, to understand how parrotfish teeth work.

Because conventional microscopes can overlook the unique orientation of crystals in tooth enamel, the team used the technique called polarization-dependent imaging contrast (PIC) mapping that Gilbert invented, which uses the photoemission electron microscopy (PEEM) Beamline 11.0.1 at the ALS. The PIC maps allowed them to visualize the orientation of individual crystals of fluorapatite, the main mineral component of parrotfish teeth.

Separate experiments used tomography (Beamline 8.3.2) and microdiffraction (Beamline 12.3.2) to further analyze the crystal orientations and strains in the teeth.

>Read more on the ALS website

Image: (extract) PIC maps acquired at the tips of four different parrotfish teeth show that they consist of 100-nm-wide, microns-long crystals, bundled into “fibers” interwoven like warp and weft fibers in fabric. These fibers gradually decrease in average diameter from 5 μm at the back of a tooth to 2 μm at the tip. Intriguingly, this decrease in size is spatially correlated with an increase in hardness and stiffness. The orientation angle of the crystals is color-coded (chart at bottom).