European XFEL – Lightsources.org

Capturing nanoparticles with two-frame X-ray movies

2026/09/042026/09/10

Two-colour X-ray pulses record the same sample at two moments in time.

One big dream of ultrafast science has been to watch changes in nanoparticles or biomolecules on their natural timescale. Experimentally, this can be realized by taking two snapshots of the same nanoscale object only femtoseconds (millionth of a billionth of a second) apart. A new capability of the European XFEL has recently enabled a big step towards the realization of this dream: the X-ray laser can produce subsequent flashes of two different colours, that are bright enough to image a particle twice within femtoseconds. However, a big challenge remained: no detector is fast enough to record the two snapshots separately—they end up on top of each other in a single image, comparable to a double-exposure photograph. Scientists now successfully employed two complementary methods to disentangle two diffraction patterns captured by the same X-ray detector. The results by an international team of researchers have been published their results in two separate articles in Nature Communications.

While both take advantage of the different colours or photon energies, one method exploits the capability of the detector to discern energy levels for each individual pixel, while the other uses mathematical reconstructions. Its inventors call the latter method Dichography. One of the leading scientists compares the technique to an extreme high-speed camera: “To my knowledge, these are the fastest nanoscale movies ever recorded, if by movie we mean multiple frames of the same object,” says Alessandro Colombo from the Department of Physics at ETH Zurich in Switzerland.

Image: A double exposure image can picture the same subject at different points in time. Disentangling the two events can be challenging. However, in this famous photograph, it can be assumed that inventor Nikola Tesla was not in the room when the electric discharge occurred.

Credit: Dickenson V. Alley. License: CC-BY-SA

More than just viscous: researchers examine movement of proteins

2026/08/072026/08/12

Study yields new insights into how proteins navigate crowded cell-like environments

How do proteins find their way through the dense crowd inside a cell? An international research team, including researchers from the University of Siegen, has investigated this question at the world’s largest X-ray laser – the European XFEL. The results of the measurements show that it is not just the viscosity of the environment that is decisive. The way the molecules influence one another also plays an important role – and can even lead to individual proteins initially moving faster than expected under certain conditions. The study has now been published in the prestigious journal Proceedings of the National Academy of Sciences (PNAS).

“Conducting research at European XFEL was a fantastic opportunity and a wonderful experience. As proteins are very small – we’re talking in the nanometre range here – short-wavelength X-rays are well suited to studying them,” says Michelle Dargasz, lead author of the study and a PhD student working with Christian Gutt, Professor of Solid-State Physics at the University of Siegen.

Image: Co-authors Michelle Dargasz (right) and Nimmi Das Anthuparambil at the ‘Materials Imaging and Dynamics’ (MID) instrument at the European XFEL, where the experiments were carried out.

Credit: University of Siegen

New fusion hub around European XFEL

2026/07/292026/07/30

German government backs hub for laser fusion in Hesse and around European XFEL

The German Federal Ministry for Research, Technology and Space (BMFTR) today announced funding for a hub for laser fusion, with sites in Hamburg/Schleswig-Holstein and Hesse. European XFEL will be at the heart of a fusion R&D campus Hamburg/Schleswig-Holstein. This campus will serve as the center of German laser fusion research and development, with the clear goal of preparing for the construction of the world’s first commercial laser fusion power plant in Germany.

The German laser fusion companies Marvel Fusion and Focused Energy, co-founders and co-shareholders of the hub, are developing the campus together with European XFEL, DESY, HZDR, the University of Hamburg, Kiel University, and the University of Rostock, along with a broad network of additional scientific and industrial partners and with the support of the states of Hamburg and Schleswig-Holstein. The hub will encompass an additional site – the Fusion Industrialization Campus in Biblis, Hesse – and incorporate satellite locations across the full Fusion State Alliance (“Länderallianz”). The BMFTR is funding the hub under the “Hubs for Fusion” funding directive, which is part of the federal government’s Hightech Agenda.

The Hamburg/Schleswig-Holstein campus focuses on laser physics, diagnostics, and materials research. European XFEL intends to expand its capabilities to enable precise measurement of laser-target interactions across a wide parameter range – a fundamental prerequisite for validating new ignition and compression concepts on the path to a fusion power plant. This infrastructure is unique in the world: the hub can draw on an established scientific base and decades of expertise from DESY in the development of high-power lasers.

Research relevant to fusion is already being carried out at the European XFEL at the existing HED-HIBEF scientific instrument. The HIBEF (Helmholtz International Beamline for Extreme Fields) consortium operates extremely powerful lasers there under the leadership of the Helmholtz Centre Dresden-Rossendorf (HZDR). Another partner in the Laser Fusion Hub will be the High Energy Density Institute (HEDI), which involves the University of Rostock.

The hub is led by Marvel Fusion and Focused Energy, together with the IFE Innovation Network e.V., an association yet to be formally established. A large number of scientific and industrial partners have expressed interest in joining – including 15 universities and research institutes, 13 industrial partners, and 3 technology transfer organizations. European XFEL, together with Hamburg and Schleswig-Holstein, will coordinate the establishment of the association.

Image: Fusion-relevant research is being conducted at the HED-HIBEF scientific instrument of European XFEL

Credit: European XFEL

Researchers watch chemistry unfold atom by atom

2026/07/132026/07/16

Study suggests a new way to follow electronic and vibrational dynamics in real time

Researchers have captured how a molecule redistributes energy after absorbing light, differentiating the roles of individual atoms in the process. They used X-ray flashes from the European XFEL to show that different atoms of the same molecule can reveal entirely different aspects of the process. The study provides clear evidence that excitation by light can enhance an atom’s sensitivity to motion of nearby atoms. The new method for following ultrafast chemical reactions at the atomic scale and in real-time can help understanding photostability in DNA, energy flow in light-harvesting materials, and other fundamental processes driven by light.

The team investigated 3-fluoropyridine, a small ring-shaped molecule. When the molecule absorbs light like a short pulse from an ultraviolet laser, it is promoted into an electronically excited state and rapidly distorts out of its original planar shape. It then passes through a so-called conical intersection: a short-lived but crucial crossing point where movements of electrons and the atoms’ cores become strongly coupled. After this point, the molecule returns to the ground state. At that moment, electronic energy is converted into vibrations. The researchers found that this conversion leaves distinct fingerprints at different atomic sites: the fluorine atom acts as a clean marker of vibrational relaxation, while the nitrogen atom, which is more directly involved in the excitation, reflects an intertwined response of electron redistribution and structural motion. “We can now see that not every atomic site tells the same story in the signals we capture from our X-ray pulses,” says Antonio Picón from the Instituto de Ciencia de Materiales de Madrid Consejo Superior de Investigaciones Científicas (ICMM-CSIC), co-author of the study. “Some atoms report where the charge is going, while others reveal how the whole molecule vibrates.”

To observe this process, the team used time-resolved X-ray photoelectron spectroscopy (tr-XPS) at the Small Quantum Systems instrument (SQS) of European XFEL. An ultraviolet laser pulse first excited the molecules, and a precisely delayed soft X-ray pulse then ionized them by removing deeply bound electrons from either the nitrogen or fluorine atoms. By measuring the energy of these emitted electrons at many different time delays, the scientists reconstructed how the local chemical environment evolved over the course of just a couple of picoseconds (trillionths of seconds). To interpret the data, the team developed advanced simulations and models.

Image: Experiment on 3-fluoropyridine: a UV pulse (purple beam from the left) excites the molecule, and a delayed X-ray pulse (white beam from the lower right) probes the nitrogen atom (purple sphere). The measurement reveals light-induced charge redistribution (purple cloud) from the perspective of a core-photoelectron from the nitrogen site (concentric rings). The fluorine atom (green sphere) can also be probed and acts mainly as a marker of vibrational dynamics.

Credit: European XFEL/Enrique Sahagun

How electrons actually behave in warm dense matter

2026/06/192026/06/24

Widely used models mispredict collective electron oscillations in warm dense aluminium, study shows

Researchers at European XFEL, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Rostock University and other collaborating institutions have used high-precision experiments to demonstrate that the most widely used models for the behaviour of electrons in warm dense matter are inaccurate. Warm dense matter is challenging to study but also of key importance for a plethora of research, including the investigation of planetary interiors, material science, and laser fusion experiments. The study has been published in Physical Review Letters.

In warm dense matter, electron density oscillates. The collective oscillations are called plasmons. They carry important information and can be observed using X-rays, resulting in scattering spectra – abstract images captured by a detector. In many experiments, these spectra are interpreted using simplified uniform electron gas models. However, the new measurements show that, for warm dense aluminium, these models consistently overestimate the plasmon energy by up to about 25 per cent (about 8 electronvolts) and fail to reproduce the full measured shape of the signal.

“Our measurements are precise enough to clearly distinguish between competing models,” says Thomas Preston of European XFEL. “That is important because these models are widely used to diagnose extreme states of matter. If the model is incorrect, that leads to inaccurately inferred properties.” The electron behaviour affects predictions of opacity, optical properties, electrical conductivity, and energy transport, for instance.

New milestone in superconducting undulator development

2026/05/292026/06/02

Successful tests confirm outstanding performance of coils

Researchers at European XFEL have reached an important milestone in developing a new generation of X-ray light sources. A set of superconducting electromagnets, produced by Bilfinger Nuclear, have proven their excellent performance, paving the way for the use of the design in future superconducting undulators. These devices will cause accelerated electrons to radiate much more effectively than current state-of-the-art technology allows. European XFEL aims to become the world’s first X-ray free-electron laser to use superconducting undulators. These undulators will unlock new research in fields such as materials science, chemistry, biology and high-energy-density science by providing X-ray pulses with significantly shorter wavelengths than have been possible at XFELs to date.

The magnetic field of undulators is designed to be highly periodic, precisely controlled, and exceptionally uniform along the electron beam path. The electromagnets examined at European XFEL consist of niobium-titanium (NbTi) wire. At the operating temperature of -269 degrees Celsius, the material is superconducting, meaning it can carry very high electrical currents with virtually no resistance. When wound into coils with extreme precision, an electromagnet is created that produces a strong magnetic field when carrying an electric current. Measurements of their magnetic field have now been completed and show that the coils successfully reached the required operating current and produced the target magnetic field of 1.82 Tesla, while maintaining the necessary field quality for X-ray generation over the entire 2-metre length of the coils.

This is important because using the devices to generate X-rays relies not only on the magnetic fields being very strong, but also on them being highly periodic. Even tiny deviations from this periodic structure affect the quality of the X-ray beam generated. The qualification tests demonstrate that the coils can meet these demanding requirements over their full two-metre length, making them the longest high-precision superconducting undulator coils ever produced and measured.

Image: The SUNDAE1 test stand and a sketch of the sledge attached to a rod with Hall probes sliding along the magnetic field axis of the SCU coils (Illustration: S. Casalbuoni et al., Front. Phys. Sec. Interdisciplinary Physics Volume 11 – 2023)

Chemical shifts help track molecules breaking apart in real time

2026/03/092026/03/11

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.

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

2026/02/112026/02/19

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.

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

2026/01/282026/01/29

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.

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

2025/11/242025/11/25

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.

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

2025/10/312025/11/06

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.”

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

2025/09/222025/10/02

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.

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

2025/08/182025/08/28

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.

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

2025/08/072025/08/08

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.

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

Credit: European XFEL / Tobias Wüstefeld)

How Molecules Break and Form Bonds

2025/08/062025/08/07

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.

2014 Nobel Prize idea used to reach super-resolution

2025/07/162025/07/16

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.

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