Modern ultrafast laser technologies have initiated a 'femtosecond revolution' revolution in chemical physics, allowing the motion of nuclei within molecules to be visualised on the femtosecond (millionth of a billionth of a second) timescale. The insights from femtochemistry experiments allow detailed probing of the mechanics underpinning chemical reactions, and are therefore invaluable for fundamental investigations into molecular structure and reactivity. This proposal aims to advance understanding of how carbonyls, a key class of organic molecules found within the earth’s atmosphere (with important implications for understanding radiative forcing and climate change), react upon excitation by ultraviolet light, using state-of-the-art ultrafast experimental techniques. Whilst this crucial photochemistry has been studied by other techniques previously, a deep understanding of the complex electronic and nuclear dynamics which control the outcomes of the possible photoreactions is, so far, elusive. Throughout the grant, three different experimental techniques (ultrafast electron diffraction, ultrafast X-ray diffraction and Coulomb explosion imaging), each offering complementary structural information, will be exploited to gain an exquisitely detailed view of this important fundamental photochemistry. By studying a series of related carbonyl molecules, insights will be gained into the broad class of carbonyl molecules as a whole. Furthermore, the results will also assess the relative applicability of these experimental techniques (which have only been facilitated by recent technological advancements in the field of free-electron laser science) to probing complex molecular photochemistry on the shortest timescales. Consequently, the results will be of wide-reaching impact both in the fields of atmospheric science and within the ever-growing multi-disciplinary community which utilizes modern free-electron lasers to record so-called 'molecular movies'.

The key to move from a mere description of static materials properties to the determination and control of functionality and chemistry lies in understanding dynamic pathways through multidimensional energy landscapes. Through my efforts over the last decade my group accomplished breakthroughs towards the required excited states selectivity and to follow dynamic pathways with resonant inelastic soft x-ray scattering (RIXS) in three aspects: Non-linear RIXS for materials science to boost scattering efficiency. Time resolved and Anti-Stokes RIXS for back-ground free detection of excited states. Sub-natural line width RIXS to map out potential energy surfaces at selected atoms. In the ERC research I link these unfolding fields and combine them with ab-initio treatment of excited states to create unprecedented back-ground free X-ray probes of excited states of matter and their dynamics. This will be femtosecond time resolved Anti-Stokes RIXS for excited state selectivity with transform limited pulses and doubly resonant soft X-ray 4 wave mixing to determine multi-center dynamics on atomic scales. The ERC grant will answer long standing questions on the governing principles of functionality, regarding chemical pathways and energy landscapes in molecules as well as phase transitions, driven phases and emergence in functional materials. These novel approaches become only now feasible through the unprecedented brilliance of Free-Electron Lasers and the efforts of my group over the last decade. The ERC grant will establish proof-of-principle at brilliant soft X-ray Free-Electron Lasers that will be followed by world leading, ideal conditions implemented at the European XFEL.

Batteries are attractive candidates for lightweight, high capacity, mobile energy storage solutions. Despite decades of research, a persistent fundamental knowledge gap prevents batteries from fulfilling their potential, because the atomistic mechanisms of charge and ion transfer across interfaces in batteries remain largely unexplored by experimental techniques. When charges move, the local arrangement of atoms changes in response to the new electronic configuration. How these changes occur has a significant impact on how efficiently and how far the charges can move, yet the time and length scales are still poorly understood. Conventional experimental probes used in battery research cannot provide the needed ultrafast time and atomic length scale resolution, nor sensitivity to changes in electronic configuration around specific atomic species. Hence, it is currently challenging to unravel the dynamic rearrangement of atoms and ions which accompany electron transfer, and in turn govern the charge transfer processes. UltraBat will close this knowledge gap by pushing further the latest development of ultra-bright and ultra-fast X-ray Free Electron Laser (XFEL) scattering and spectroscopy techniques together with visible ultrafast spectroscopy to study charge transfer between different redox centres in Li-rich layered intercalation compounds and at the solid/liquid interface. Advances in NMR spectroscopy will reveal local ordering and lithium interfacial dynamics on the nanometer scale. Coupled with predictions of experimental observables from a new framework for atomic-scale simulations of the electrochemical interface and transport mechanisms, we will reveal phenomena driving diffusion of ions in complex electrode materials. This will provide the insight required for transformational approaches to control the redox reactions (e.g. electron transfer) that are common to many energy-related processes, including batteries, photovoltaics, and water-splitting systems.

One of the highlights of the European research infrastructure landscape is the world's most powerful X-ray-laser, the European XFEL. The ELBEX (Extracted Lepton Beam at the European XFEL) proposal builds on this strength and will set up new opportunities for European scientists and innovators, by providing an extracted high energy electron beam for experiments. With ELBEX we propose a pathfinder project to demonstrate the feasibility of such a facility at the European XFEL. This unique new possibility would strengthen the global competitiveness of the European Research Area and create opportunities for new user groups. The high energy, high charge density and excellent quality of the electron beam, if brought into interaction with a strong laser beam, opens up the study of a range of scientific topics, most prominently, of strong field Quantum Electrodynamics (QED). For the first time, the Schwinger limit for the electromagnetic field strength, at which non-perturbative QED effects become relevant, could be reached experimentally in this facility. Studying the particles created in the photon beam dump opens up the possibility to search for feebly interacting particles, complementing current or planned experiments like FASER II or SHiP. In addition, the electron beam itself is at the centre of a range of highly relevant and ambitious experiments in the area of accelerator science and detector science. Within the ELBEX project, the installation of a facility to extract an electron beam from the European XFEL using a fast kicker magnet and to transport it into a multi-purpose experimental area will be prepared. On the condition that a positive decision by the European XFEL council is reached to grant an extended 12-week XFEL shutdown, the installation of the ELBEX facility is an option.

The European XFEL has just entered user operation. With its unparalleled peak brilliance and repetition rate, European XFEL has the potential to further applications in single particle imaging (SPI), thus far limited to large viral particles at X-ray Free-Electron Lasers (XFEL). SPI will allow imaging protein complexes without the need for crystallization. This eventually renders transient conformational states accessible for high resolution structural studies yielding molecular movies of biomolecular machines. A major bottleneck is the wealth of data required to reconstruct a single structure leading to long processing times. This is currently also a problem in electron microscopy (EM). MS SPIDOC will overcome this data challenge by developing a native mass spectrometry (MS) system for sample delivery, named X-MS-I. It will provide mass and conformation selected biomolecules, which are oriented along their dipole axis upon imaging. This will enable structural reconstruction from much smaller datasets speeding up the analysis time tremendously. Moreover, the system features low sample consumption and a controlled low background easing pattern identification. The main objectives of the project are: • Deliver mass and conformation separated biomolecules for SPI. • Orient proteins for SPI. • Image protein complex unfolding • Exploit potential of protein orientation for other applications The MS SPIDOC consortium combines internationally leading expertise in different fields relevant to the project: Instrument design and development, computer simulations as well as working with biomolecules in the gas phase and on SPI are combined to implement the novel sample environment at the next generation XFEL facility. New components and methods will be opened to the market and thereby strengthen the European Research Area (ERA) and industry. This early stage high-risk project will give rise to a new technology with major impact on how to derive structures of biomolecules.