Category: European XFEL

Chemical shifts help track molecules breaking apart in real time

Chemical shifts help track molecules breaking apart in real time

Ultrafast X-ray photoelectron spectroscopy at European XFEL offers a new way to watch reactions, atom by atom.

When molecules fall apart, their electric charge doesn’t stay put—it rearranges as bonds stretch and break. An international team of scientists has now tracked these ultrafast changes in the small molecule fluoromethane (CH₃F). It was the first time that the Small Quantum Systems (SQS) instrument at European XFEL could deliver detailed insights into transient states during chemical reactions. These intermediate states, that only exist temporarily while the reaction is ongoing, are often the key drivers of chemistry and therefore crucial to understand. Over the long term, that kind of insight can support progress in areas such as atmospheric science (where sunlight-driven reactions and fragmentation pathways shape air chemistry), as well as the study of complex molecular systems including biomolecules and proteins, where local excitation and charge transfer can trigger structural change.

In the experiment, the researchers first triggered the reaction with an optical laser pulse. Next, they used the X-ray laser pulses that the European XFEL produces, to eject an electron from the core of either the fluorine or the carbon atom in the molecule. They measured the electron’s kinetic energy, which reveals how strongly it was bound inside the atom. That binding energy is extremely sensitive to the local electrical environment, producing so-called “chemical shifts” that act like a fingerprint of the charge distribution surrounding the atom from which the electron has been ejected. With an overall time resolution of about 35 femtoseconds (trillions of times shorter than the blink of an eye), the team could follow changes separately at two atomic sites, carbon and fluorine, inside the same molecule. The method is called time-resolved X-ray photoelectron spectroscopy (tr‑XPS).

“Core-level photoelectron spectroscopy tells us what is happening at a specific atom,” says Michael Meyer, lead scientist at the Small Quantum Systems (SQS) instrument at European XFEL. “By probing carbon and fluorine independently, we can see when different fragments appear and how the charge distribution evolves during dissociation. 

Read more on the European XFEL website

Image: Illustration of the pump–probe experiment on fluoromethane (CH₃F): Shortly after an ultrashort optical laser pulse (red) has ionized the molecule and triggered bond breaking, a femtosecond X-ray pulse (blue/white) ejects a core electron (green clouds) from the fluorine atom (green ball). By measuring the electron’s kinetic energy, the experiment tracks time-dependent ‘chemical shifts’ that reveal how the local electronic environment changes as the molecule dissociates – in this case the departure of a hydrogen atom (white ball).

Credit: Illustration: European XFEL

European XFEL celebrates a successful restart

European XFEL celebrates a successful restart

European XFEL today celebrated the restart of the world’s largest X-ray laser with a ceremony attended by Hamburg’s Senator for Science Maryam Blumenthal and Guido Wendt, State Secretary in Schleswig-Holstein’s Ministry of Education, Science, Research and Culture. This was preceded by a so-called Long Installation and Maintenance Period (LIMP) with maintenance work and numerous upgrades to the infrastructure in underground tunnels and the scientific instruments on the European XFEL campus.

Employees of European XFEL and DESY, who were significantly involved in the extensive work, watched as Blumenthal and Wendt started the electron accelerator with a click of a mouse. Electron packets now speed again through the accelerator section to the so-called dump after about two-thirds of the 3.4-kilometre-long facility. The remaining parts of the X-ray laser, where the X-ray light is generated using the accelerated electrons, and the experiment stations will go into operation in the coming days and weeks. After more than seven months, the facility will be available to researchers again from mid-April.

Innovations for scientific excellence

At the ceremony in the Lighthouse visitor centre, European XFEL Managing Director Prof. Thomas Feurer emphasized the importance of the modification and upgrade work for the long-term performance, reliability and scientific excellence of the large-scale research facility. In addition to the successful maintenance work, for which the accelerator, which normally operates at minus 271 degrees Celsius, was warmed to room temperature and then cooled down again, teams from European XFEL and the DESY research centre installed numerous technical innovations to further expand the research options at the X-ray laser. Important upgrades include the new GUN5 electron source, which enables a pulse rate that is around 30 percent higher, and the expansion of beamlines and instruments for attosecond experiments, which can be used to observe ultrafast processes such as the formation of chemical bonds. In addition, preparatory work has been completed for the installation of superconducting undulators, which will deliver particularly short and highly intense X-ray pulses with very short wavelengths, enabling researchers to achieve even better resolution, among other things.

Read more on the European XFEL website

Image: Thomas Feurer emphasized the smooth cooperation between European XFEL and DESY, involving many teams from different disciplines.

Credit: European XFEL

Lasing achieved with hard X-rays in a resonator

Lasing achieved with hard X-rays in a resonator

Novel “XFELO” laser system produces razor-sharp X-ray light

For the first time, researchers have amplified X-ray light multiple times in a resonator cavity, in a way highly similar to traditional lasers. With great success: the new technique delivers extremely energetic X-ray pulses for high-precision experiments. This development opens up entirely new possibilities for research in physics, chemistry, or biology. The system is called “XFELO”. Researchers from European XFEL, DESY and Hamburg University have published their findings in the latest edition of the journal Nature. 

The team of engineers and scientists have shown for the first time that a hard-X-ray cavity can provide net X-ray gain, with X-ray pulses being circulated between crystal mirrors and amplified in the process, much like happens with an optical laser. The result of the proof-of-concept at European XFEL is a particularly coherent, laser-like light of a quality that is unprecedented in the hard X-ray spectrum. Lasing inside a cavity had been challenging to achieve with short-wavelength X-rays for a variety of reasons, including – on a basic level – that the nature of the light makes it difficult to reflect the beam at large angles. The “XFELO” (short for: X-Ray Free-Electron Laser Oscillator) technique opens new perspectives for scientific investigations, from ultrafast chemical reactions to detailed analyses of the smallest biological structures.

Read more on the European XFEL website

Image: Illustration of the XFELO system: a hard X-ray pulse (red) is reflected by a set of diamond mirrors and oscillates through arrays of magnets, so called undulators. On each roundtrip the pulse meets a new electron bunch (blue), which emits X-rays while passing through the undulators on a slalom course.

Credit: European XFEL

LEAPS chairmanship transferred to Thomas Feurer

LEAPS chairmanship transferred to Thomas Feurer

Consortium set to increase influence in Brussels and broaden funding base

At the 8th LEAPS Plenary Meeting, Prof. Thomas Feurer was welcomed as the 2026 Chair of the League of European Accelerator-based Photon Sources. Feurer is also Chairman of the Management Board of European XFEL and succeeds Prof. Jakub Szlachetko from the National Synchrotron Radiation Centre SOLARIS in Krakow, Poland. 

“It is an honour to be chairing LEAPS,” said Feurer, who attended the meeting remotely. “I am looking forward to continuing the excellent work that has been done here in recent years.” A significant milestone for LEAPS under Feurer’s leadership will be its registration as an international non-profit association under Belgian law in spring 2026. “This will result in stronger visibility and influence in Brussels and beyond, enhancing our ability to form cross-sectoral partnerships in Europe”, Feurer explained.

As a non-profit entity, LEAPS will facilitate collaboration agreements in science and technology between its members and help coordinate funding. Feurer is looking to broaden the funding base for European photon science by pursuing multi-partner opportunities, including partnerships with industry consortia. While building an increased presence at EU level, he also intends to align LEAPS more closely with national roadmaps.

The LEAPS chairmanship was ceremonially handed over at the consortium meeting. Prof. Serguei Molodtsov, Scientific Director of European XFEL, accepted the symbolic baton on Thomas Feurer’s behalf. 

Read more on the European XFEL website

Image: Prof. Serguei Molodtsov, Scientific Director of European XFEL, accepts the symbolic chairmanship baton on Thomas Feurer’s behalf

Credit: Joanna Kowalik

Tailwind for fusion research in Germany

Tailwind for fusion research in Germany

High-Tech Agenda Germany to strengthen fusion-related research. European XFEL will be a vital partner.

With the High-Tech Agenda Germany, the German government has set the course for the advancement of fusion-related research in Germany. The action plan ‘Germany on the way towards a fusion power plant’ defines measures to build the world’s first fusion power plant in Germany.

Nuclear fusion, as it takes place in the sun, promises an almost inexhaustible source of energy. At its core, it involves the fusion of lighter atoms such as hydrogen, deuterium and tritium into heavier atoms such as helium. This produces huge amounts of energy, which is to be harvested in a power plant.

The world’s largest X-ray laser, the European XFEL in Schenefeld near Hamburg, is predestined for investigating fundamental processes of fusion. In particular, researchers at European XFEL want to contribute to investigating the critical early phases of fusion-related reactions. Its instruments are equipped with powerful lasers that generate the very high energy densities required to create plasma, an extremely hot state of matter. Using the extremely short and intense X-ray laser flashes of the European XFEL, the researchers would be able to analyse the reactions taking place step by step. This would provide extremely detailed images of the inside of fusion experiments, right down to the atomic level.

“With our X-ray laser, we can precisely investigate how fusion-related processes take place,” explains Prof Thomas Feurer, Managing Director and Chairman of the Management Board of European XFEL. “This enables researchers to better understand the complex processes and better predict the conditions under which a fusion reaction begins and how it can be optimised.”

“The European XFEL was built with a future-proof design, enabling it to continuously expand its capabilities to meet emerging scientific challenges,” so Feurer. “This forward-looking approach positions us to contribute within a short time to the next level of fusion research.”

Read more on the European XFEL website

Image: Thomas Feurer giving an outlook on how the world’s largest X-ray laser can significantly support research in the field of fusion energy

Credit: European XFEL

European XFEL receives new electron source

European XFEL receives new electron source

The European XFEL, the world’s largest X-ray laser, is taking another leap forward. On 17 September, a brand-new electron source, known as “GUN5”, was delivered to Hamburg after years of development and rigorous testing at DESY’s Photo Injector Test Facility (PITZ) in Zeuthen. During the current extended maintenance period, the source is being installed in the accelerator’s injector – a critical upgrade that will directly enhance the laser’s experimental capabilities.

“The next generation of electron source for our accelerator is crucial because it enables higher stability and efficiency, directly advancing accelerator performance, scientific discovery, and underlining European XFEL’s role as a global leading research facility,” says Thomas Feurer, Director and Chairman of the Management Board of European XFEL, underlining the importance of this component. The future provision of even brighter, faster and more stable X-ray flashes by the European XFEL from the beginning of 2026 will enable scientists from all over the world to study matter at the atomic level even better – from the dynamics of chemical reactions and the behaviour of quantum materials to the structures of viruses or biomolecules. “With the modernised accelerator, European XFEL will continue to push the boundaries of science and technology and offer researchers unprecedented opportunities to explore the building blocks of life and our world,” states Feurer.

For a free-electron laser to work, one factor is key: the density of electrons in each accelerated bunch. The denser the bunch, the more efficiently it can interact with the self-generated X-ray light in the undulator, creating the ultrashort, brilliant flashes of light that make the European XFEL unique.

Remarkably, the crucial parameters are set within the very first 30 centimetres of acceleration – a tiny section that ultimately determines the success of experiments taking place over three kilometres away at the facility in Schenefeld.

Developing reliable and powerful electron sources – called “guns” – has therefore been essential to building and operating free-electron lasers. At European XFEL and its sister facility FLASH, both based on superconducting accelerator technology, these sources have been a cornerstone since the 1990s.

Inside an XFEL gun, an intense laser beam frees electrons from a specially coated metal surface, the cathode, via the photoelectric effect. These electrons are then rapidly accelerated by strong radio frequency fields in a copper cavity. The process has to happen in fractions of a second: if electrons spread out too much, the bunch density is lost. The rapid acceleration process benefits from a relativistic effect that limits the repulsion between the electrons. This allows the researchers to keep the electron bunches very compact and therefore the charge density very high.

The development of the sources began in the 1990s, together with research into superconducting accelerator technology, when DESY decided to build a free-electron X-ray laser. The new generation, GUN5, builds on these decades of expertise at PITZ in Zeuthen and DESY in Hamburg. While the fourth generation (GUN4) has been in use since the start of European XFEL operations in 2017, plans for improvements were already under discussion during commissioning. “Out of these discussions came the fifth generation, with a refined shape, integrated field probes, enhanced cooling, improved mechanics for swapping cathodes, and a double input window. These advancements allow the gun to be more stable and reliable in the future,” says Frank Stephan, leader of PITZ.

Read more on European XFEL website

Image: The next generation of electron source was delivered to the injector building of the European XFEL on the DESY campus. It enables higher stability and efficiency, directly advancing accelerator performance.

Credit: European XFEL, Sven Kamin

Looking into the tiniest deformations of atomic lattices

Looking into the tiniest deformations of atomic lattices

When light hits solar cells, so-called electron-hole pairs are created: the electrons are excited and can move almost freely in the material – i.e. to generate electricity. The electrons will leave ‘positive gaps’, so-called holes, in the semiconductor material. They can also move through the material. Both electrons and holes carry an electrical charge. They deform the surrounding atomic lattice on their way through the material slightly.

An international research team at European XFEL has now been able to directly observe this very weak effect for the first time. “With the help of extremely fast flashes from European XFEL’s X-ray laser, we were able to visualise this barely noticeable change”, explains Johan Bielecki, scientist at the Single Particles Biomolecules and Clusters/Serial Femtosecond Crystallography (SPB/SFX) instrument at European XFEL, where the experiment was carried out. According to the researchers, this could be an important step in the development of new materials for solar cells or light-emitting diodes, for example.

A so-called quantum dot of caesium, lead and bromine (CsPbBr3) studied by the scientists was only a few millionths of a millimetre in size. A quantum dot is a tiny object whose properties can no longer be described classically, but only with the help of quantum physics.

When light hits this quantum dot, electron-hole pairs are created. Due to their electrical charge, both the electron and the hole pull on the atoms in the crystal – as if two people were tugging on a net and deforming it. In this way, the pair of particles creates a kind of ‘dent’ in the crystal. In physics, this state is called an exciton-polaron.

The lattice deformation only affects a few atoms – but it is decisive for the optical and electronic properties of the material. “The better we understand the deformation, the better we can try to develop improved materials, for example for more efficient displays or more powerful sensors,” says Zhou Shen from the Max Planck Institute for the Structure and Dynamics of Matter and lead author of the study.

A particularly precise method is required to detect the lattice deformation at all. The researchers used the European XFEL in Schenefeld near Hamburg – the largest X-ray laser in the world. It emits extremely short and intense X-ray flashes. It enables images to be captured within femtoseconds – in other words, within a quadrillionth of a second. “It’s like observing the movement of atoms with a high-speed camera,” says Bielecki.

Read more on European XFEL website

Image: Johan Bielecki at the Single Particles Biomolecules and Clusters/Serial Femtosecond Crystallography (SPB/SFX) instrument of European XFEL, where the experiment was carried out.

Credit: European XFEL

Revealing quantum fluctuations in complex molecules

Revealing quantum fluctuations in complex molecules

Due to the Heisenberg uncertainty principle of quantum physics, atoms and molecules never come completely to rest, even in their lowest energy state. Researchers at European XFEL in Schenefeld near Hamburg have now been able to directly measure this quantum motion in a complex molecule for the first time. For this, however, as they report in the journal Science, they had to make the molecule explode in the process.

Absolute standstill only exists in classical physics. In the quantum world, even the ground state with the lowest energy is characterised by persistent fluctuations. This is due to a quantum-mechanical principle discovered by Werner Heisenberg a hundred years ago during the development of quantum mechanics. The so-called zero-point fluctuations are a quantum effect that prevents atoms from remaining precisely at a fixed position, even at temperatures near absolute zero. At European XFEL in Schenefeld, researchers have now made the previously invisible directly observable – and the quantum world a bit more tangible.

An international team led by Rebecca Boll from the SQS (Small Quantum Systems) instrument at European XFEL in Schenefeld, Ludger Inhester from the DESY research centre, and Till Jahnke from the Max Planck Institute for Nuclear Physics in Heidelberg, succeeded in visualising the collective trembling of an entire molecule. Using a sophisticated experiment and refined data analysis, they were able to measure the quantum fluctuations of the 2-iodopyridine molecule (C5H4IN), which consists of eleven atoms – a milestone in molecular imaging. They describe their work in the renowned journal Science.

The researchers employed a method as spectacular as its name: Coulomb Explosion Imaging. The ultrashort, extremely intense X-ray laser pulses of European XFEL strip numerous electrons from the atoms of individual 2-iodopyridine molecules very rapidly. The remaining atomic cores become positively charged, repelling each other. The result resembles a microscopic big bang: the atomic cores fly apart in an explosion.

Read more on European XFEL website

Image: Visualisation of collective quantum fluctuations of a complex 2-iodopyridine molecule

Credit: European XFEL / Tobias Wüstefeld)

How Molecules Break and Form Bonds

How Molecules Break and Form Bonds

Researchers at European XFEL in Germany have tracked in real time the movement of individual atoms during a chemical reaction in the gas phase. Using extremely short X-ray flashes, they were able to observe the formation of an iodine molecule (I₂) after irradiating diiodomethane (CH₂I₂) molecules by infrared light, which involves breaking two bonds and forming a new one. At the same time, they were able to distinguish this reaction from two other reaction pathways, namely the separation of a single iodine atom from the diiodomethane, or the excitation of bending vibrations in the bound molecule. The results provide new insights into fundamental reaction mechanisms that have so far been very difficult to distinguish experimentally.

So-called elimination reactions in which small molecules are formed from a larger molecule are central to many chemical processes—from atmospheric chemistry to catalyst research. However, the detailed mechanism of many reactions, in which several atoms break and re-form their bonds, often remains obscure. The reason: The processes take place in incredibly short times—in femtoseconds, or a few millionths of a billionth of a second.

An innovative experimental approach was now used at the SQS instrument at European XFEL to visualize such reaction dynamics. The researchers irradiated diiodomethane molecules with ultrashort infrared laser pulses, which triggered the molecular reactions. Femtoseconds later, intense X-ray flashes shattered the molecules, causing their atomic components to fly apart in a “Coulomb explosion.” The trajectories and velocities of the ions were then recorded by a detection device called the COLTRIMS reaction microscope (COLd Target Recoil Ion Momentum Spectroscopy)—one of the detection instruments at the SQS experimental station that is made available to users.

“Using this method, we were able to precisely track how the iodine atoms assemble while the methylene group is cleaved off,” explains Artem Rudenko from Kansas State University, USA, the principal investigator of the experiment. The analysis revealed that both synchronous and asynchronous mechanisms contribute to the formation of the iodine molecule—a result that was supported by theoretical calculations.

Remarkably, “Although this reaction pathway only accounts for about ten percent of the resulting products, we were able to clearly distinguish it from the other competing reactions,” explains Rebecca Boll from the European XFEL’s SQS (Small Quantum Systems) instrument in Schenefeld near Hamburg. This was made possible by the precise selection of specific ion fragmentation channels and their time-resolved analysis.

Read more on European XFEL website

2014 Nobel Prize idea used to reach super-resolution

2014 Nobel Prize idea used to reach super-resolution

In a leap forward for atomic-scale imaging, researchers have introduced a novel X-ray technique that could transform our understanding of electron motion at the microscopic level. This cutting-edge method, developed by an international team of scientists, uses the unique properties of European XFEL at Schenefeld near Hamburg, Germany—the largest X-ray laser in the world—to capture detailed snapshots of atomic interactions. The results of this research were now published in Nature.

The technique, called stochastic Stimulated X-ray Raman Scattering (s-SXRS), turns noise into valuable data, offering snapshots of the electronic structures of atoms. This advancement sets the stage for breakthroughs in chemical analysis and materials science.

Researchers from the U.S. Department of Energy’s (DOE) Argonne National Laboratory, the Max Planck Institute for Nuclear Physics, of European XFEL and others developed this innovative approach to X-ray spectroscopy, achieving unprecedented detail and resolution.

“For a long time, chemists have dreamed of seeing how electrons move when they’re in excited states, as these movements are what drive chemical reactions,” says Linda Young, an Argonne Distinguished Fellow and professor at the University of Chicago. “Our technique brings us closer to realizing that dream.”

The key innovation is a super-resolution technique that greatly improves the detail in X-ray spectroscopy, a method for studying electron placement around atomic centres. This advancement helps scientists identify closely spaced energy levels in atoms, offering a clearer view of their electronic structures, which determine chemical properties.

“Think of it like upgrading from a standard-definition television to an ultra-high-definition screen,” Young explains. “We’re now able to see the fine details of electronic motion that were previously blurred or invisible.”

The practical applications of stochastic Stimulated X-ray Raman Scattering are wide-ranging. For example, it can provide insights into how chemical bonds form or break, offering a deeper understanding of fundamental processes relevant to chemical analysis. This knowledge is essential for developing new materials with specific electronic properties, impacting industries like electronics and nanotechnology.

The researchers directed the X-ray pulses of European XFEL through neon gas and used a spectrometer to collect the resulting radiation. The small, 5-millimeter gas cell was designed by the Max Planck Institute for Nuclear Physics The intense beam created tiny holes in the cell’s entrance and exit windows, allowing the X-rays to pass through to a grating spectrometer—a device that separates light into its different wavelengths—provided by collaborators from Uppsala University in Sweden. The European XFEL experts have taken on a vital role in coordinating the installation and performing thorough pre-experimental testing. “This ensured optimal focusing conditions, which were crucial for efficiently acquiring a large amount of data during the experiment” explains Michael Meyer, group head of the Small Quantum Systems (SQS) instrument at European XFEL and a researcher in the Cluster of Excellence ‘CUI: Advanced Imaging of Matter’.

As the X-rays pass through the gas, they amplify the Raman signals—a type of X-ray fingerprint that provides information about the excited electronic states of atoms or molecules—by nearly a billion-fold. This amplified signal provides detailed information about the electronic structure of the gas on a femtosecond timescale, or one quadrillionth of a second. By analysing the relationship between the incoming pulses and the resulting Raman signals, scientists can create a detailed energy spectrum from many individual snapshots, rather than scanning slowly across different energy levels.

“The large number of pulses in each X-ray flash not only boosts the measurement signal but also holds the key to the highest spectral resolution by averaging over many photon impacts on the detector at once,” says Thomas Pfeifer from the Max Planck Institute for Nuclear Physics.

“This approach, pinpointing the centre position of broad but distinct spectral spikes much more precisely than the width of the spikes, is similar to the super-resolution microscopy technique that won the 2014 Nobel Prize in chemistry”, Pfeifer adds.

Read more on European XFEL website

Image: An incoming X-ray light wave (left) made up of a chaotic distribution of very fast spikes interacts with atoms (purple dots) in a gas to amplify specific spikes (right) in the light wave.

Credit: Illustration by Stacy Huang/Argonne National Laboratory

Structure of liquid carbon measured for the first time

Structure of liquid carbon measured for the first time

With the declared aim of measuring matter under extreme pressure, an international research collaboration headed by the University of Rostock and the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) used the high-performance laser DIPOLE 100-X at European XFEL for the first time in 2023. With spectacular results: In this initial experiment they managed to study liquid carbon – an unprecedented achievement, as the researchers report in the journal Nature (DOI: 10.1038/s41586-025-09035-6). 

Liquid carbon can be found, for example, in the interior of planets and plays an important role in future technologies like nuclear fusion. To date, however, only very little was known about carbon in its liquid form because in this state it was practically impossible to study in the lab: Under normal pressure carbon does not melt but immediately changes into a gaseous state. Only under extreme pressure and at temperatures of approximately 4,500 degrees Celsius – the highest melting point of any material – does carbon become liquid. No container would withstand that.

Laser compression, on the other hand, can turn solid carbon into liquid for fractions of a second. And the challenge was to use these fractions of a second to take measurements. In a previously unimaginable way, this has now become reality at the European XFEL, the world’s largest X-ray laser with its ultrashort pulses, in Schenefeld, near Hamburg.

Unique measuring technology in this combination

The unique combination of the European XFEL with the high-performance laser DIPOLE100-X was crucial for the success of the experiment. It was developed by the British Science and Technology Facilities Council and made available to scientists from all over the world by the HIBEF User Consortium (Helmholtz International Beamline for Extreme Fields). A community of leading international research institutions at the HED-HIBEF (High Energy Density) experimental station at European XFEL has now combined powerful laser compression with ultrafast X-ray analysis and large-area X-ray detectors for the first time.

In the experiment, the high-energy pulses of the DIPOLE100-X laser drive compression waves through a solid carbon sample and liquefy the material for nanoseconds, that is, for a billionth of a second. During this nanosecond, the sample is irradiated with the ultrashort X-ray laser flash of the European XFEL. The carbon atoms scatter the X-ray light – similar to the way light is diffracted by a grating. The diffraction pattern allows inferences to be drawn about the current arrangement of the atoms in the liquid carbon.

The whole experiment only lasts a few seconds but is repeated many times: every time with a slightly delayed X-ray pulse or under slightly different pressure and temperature conditions. Many snapshots combine to make a movie. Researchers have thus been able to trace the transition from solid to liquid phase one step at a time.

Read more on European XFEL website

Image: Groundbreaking experiment at European XFEL: Research team measured structure of liquid carbon for the first time

Credit: Martin Kuensting / HZDR

A pioneering spectrometer for hard X-rays

A pioneering spectrometer for hard X-rays

Researchers at the European XFEL have developed a new device for X-ray measurements at high photon energies–a so-called Laue spectrometer. It enables X-ray light with photon energies of over 15 kiloelectronvolts to be detected with improved efficiency and highest precision. This is important for researching technically significant materials that, for example, transport electricity without losses or ensure that chemical processes run more efficiently.

To unravel the secrets of the world of atoms, molecules and materials in general, scientists often use special measurement devices known as spectrometers. They work by recording the light that objects emit. From the way in which the objects do that, researchers learn a lot about the physical processes that take place in the materials. Particularly revealing is the research with X-ray light, which penetrates deeply in matter and provides information specific to each atomic species. This light is invisible to our eyes, but can be detected and measured using special spectrometers.

The main components of these devices are usually extremely precisely cut crystals made of silicon or germanium. Traditionally, the X-ray spectrometers work in what is known as Bragg geometry: The X-ray light hits the crystal and is then diffracted by the atomic planes parallel to the surface, similarly as mirrors reflect visible light. From the direction and intensity of the scattered radiation, the researchers can draw conclusions about the electronic properties of the materials they are analysing.

A unique characteristic of European XFEL is the ability to provide X-ray light with very high energy. However, as the energy of the X-rays increases, the interaction with the crystals becomes smaller, making the measurements challenging. In this high photon energy regime, a large proportion of the X-ray light simply passes through the crystal unused, which is why the performance of X-ray spectrometers using these analysers, known as Johann or Von Hamos spectrometers, decreases rapidly with increasing X-ray energy. They usually only work well up to a photon energy of around 15 kiloelectronvolts (keV).

Read more on European XFEL website

Image: Contrary to regular spectrometer the new Laue spectrometer is diffracting the X-ray beams (red arrows) by atomic layers perpendicular to the surface.

X-ray snapshot: How light bends an active substance

X-ray snapshot: How light bends an active substance

With the help of the world’s most powerful X-ray laser, European XFEL, a research team led by Goethe University Frankfurt and the research centre DESY has achieved an important breakthrough: Using the example of the pharmaceutically active substance 2-thiouracil, they applied a long-established imaging technique to complex molecules for the first time. Although 2-thiouracil is no longer applied therapeutically, it is part of a group of chemically similar active substances that are used today as immunosuppressants or cytostatics. The study shows how UV radiation deforms 2-thiouracil, making it dangerously reactive.

Many biologically important molecules change shape when stimulated by UV radiation. Although this property can also be found in some drugs, it is not yet well understood. Using an innovative technique, an international team involving researchers from Goethe University Frankfurt, the European XFEL in Schenefeld and the Deutschen Elektronen-Synchrotron DESY in Hamburg has elucidated this ultra-fast process, and made it visible in slow motion, with the help of X-ray light. The method opens up exciting new ways of analysing many other molecules.

“We investigated the molecule 2-thiouracil, which belongs to a group of pharmaceutically active substances based on certain DNA building blocks, the nucleobases,” says the study’s last author Markus Gühr, the head of DESY’s free-electron laser FLASH and Professor of Chemistry at University of Hamburg. 2-thiouracil and its chemically related active substances have a sulphur atom, which gives the molecules its unusual, medically relevant properties. “Another special feature is that these molecules become dangerously reactive when exposed to UV radiation.” Studies indicate an increased risk of skin cancer due to this effect.

To better understand what happens during such processes, the research team used an already well-established method, bringing it to a new level by applying the technical possibilities available today. “Coulomb explosion imaging involves irradiating a molecule with intense X-ray pulses, which knock out electrons,” explains Till Jahnke, Professor of Experimental Atomic and Molecular Physics at Goethe University and the study’s first author. “Thereby, the molecule charges up positively and thus becomes unstable, so that it is torn apart within fractions of a second.” By tracking the direction in which the various fragments of the molecule – the atoms – fly apart, it is possible to derive information about the molecule’s structure. 

Read more on European XFEL website

Image: The SQS instrument’s COLTRIMS reaction microscope was used to analyze the structural changes of the 2-thiouracil molecule at the European XFEL.

Credit: European XFEL

On the hunt for axions

On the hunt for axions

New X-ray experiment at the European XFEL could solve some of the mysteries of physics

Researchers at European XFEL, together with colleagues from the UK Science and Technology Facilities Council (STFC), the University of Oxford and other research institutions, have been searching for a hypothetical particle that could potentially explain the dark matter of the universe. The experiment is described in a study published in Physical Review Letters.

The researchers hunted for so-called axions at the High Energy Density instrument HED/HiBEF at European XFEL. Axions are tiny and incredibly light hypothetical particles. They are intended to explain, for example, why neutrons, which make up atomic nuclei alongside protons, have no electric dipole moment, even though the nuclear building blocks consist of even smaller charged particles known as quarks. This could also be an indication of new physics beyond the standard model. Furthermore, axions are a natural candidate for dark matter, the mysterious substance that makes up most of the structure of the universe.

The researchers used European XFEL in Schenefeld near Hamburg, the largest and most powerful X-ray laser in the world for their experiments. They channelled the intense X-ray beam of European XFEL through thin plates of germanium crystals. These have strong electric fields inside. For moving particles, this appears like an extremely strong magnetic field of around 1000 Tesla. This enables photons to transform themselves into axions and back again.

Read more on the European XFEL website

Image: Axion search at the HED/HiBEF instrument of European XFEL

Credit: European XFEL

Young Scientist Award for Patrick Heighway

Young Scientist Award for Patrick Heighway

“Patrick Heighway deserves the prestigious prize for his pivotal role in measuring X-ray diffraction at extreme pressures and temperatures at the HED-HiBEF Instrument”, says Emma McBride from Queen’s University, Belfast and chairperson of the User Organization Executive Committee (UOEC).

His work combines experimental data with molecular dynamics simulations to provide critical insight into the nature of release pathways of shock compressed materials, kinematics of plasticity, and the fundamental interaction of grains in compressed polycrystalline materials. This work is important for many different fields, including geophysics, fundamental material science, shock and plasma physics, the search for novel materials, and understanding pathways to fusion energy.

The European XFEL Young Scientist Award recognises young researchers who are at the beginning of their career but are already making outstanding contributions to research at the European XFEL.

The winner will receive a monetary award of 2,000 Euro and was invited to give a talk as part of the plenary session of the European XFEL User Meeting on 21 January 2025 in Hamburg.

For the first time, the European XFEL User Organization Executive Committee awards as well prizes to posters presented this year at the European XFEL Users’ Meeting about exciting research performed with radiation from European XFEL. Poster prizes were awarded to Daniele Ronchetti (CFEL), Calum Prestwood and Carolina Camarda (both European XFEL).

Their topics were “Elastic scattering enhancement via transient resonances” (Ronchetti), “Tracking atomic populations and transitions in x-ray heated mid-Z transition metals” (Prestwood), and “Electronic properties of Ferropericlase (Mg,Fe)O obtained from dynamic compression experiments using DiPOLE100-X at European XFEL” (Camarda).

Read more on European XFEL website

Ryszard Sobierajski new Council vice-chair

Ryszard Sobierajski new Council vice-chair

At the recent meeting of the European XFEL Council, Dr hab. Ryszard Henryk Sobierajski was elected as new vice-chair of the European XFEL’s highest governing body. He will follow by the end of the year Prof. Dr James (Jim) Henderson Naismith.

“We thank Jim for many years of inspiring contributions as European XFEL’s vice-chair,” says Thomas Feurer, Managing Director and Chair of the Management Board of European XFEL. “And we heartily welcome our well-known colleague Ryszard.”

“Ryszard is a profound expert of research with synchrotron light and free electron-lasers, and an experienced science manager,” adds Federico Boscherini, Chair of the European XFEL Council.

Sobierajski takes up his office with effect from 1 January 2025 and for a period of two years. He is Associate Professor at the Institute of Physics of the Polish Academy of Sciences, Warszawa, Poland and since January 2020 one of the Polish delegates to the European XFEL council. Additionally, he is an expert on the Proposal Review Panel for the HED instrument at European XFEL–most of the time as its chair.

Read more on XFEL website

Image: The coming vice-chair of the European XFEL Council, Ryszard Sobierajski