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Photon sources, such as table-top lasers, synchrotron X-rays and free-electron lasers (FELs), can be used to explore and understand the structure of materials through photon-matter interactions. Short wavelength and coherent photons generated, when relativistic electrons travel through undulator, from FELs are tunable and compressible to few femtosecond pulses to take snapshots of structures in order to study the time-dependent interactions and dynamics of different materials. These facilities are becoming increasingly popular in diverse research fields, because of their tunability and high spatial and temporal resolution.
In this collection, we showcase recent articles published in Nature Communications on FEL generation and characterization and their application in fundamental studies of light-matter interaction. These research papers include FEL instrumentation and techniques, investigations on photoionization and ultrafast processes in atomic and molecular physics, chemical and physical properties of condensed matter systems, and probing of structure and dynamics of biological samples. This collection highlights the increasingly significant role FELs are having on research across a diverse range of subject areas and Nature Communications’ role as a suitable platform in publishing such multidisciplinary works.
Two-colour X-ray free electron laser is a powerful tool for pump–probe measurements, but currently constrained by limited tunability. Here, Ferrari et al. develop a configuration that allows tuning both the pump and the probe to specific electronic excitations, providing element selectivity.
It is essential to understand the effect of molecular vibration on charge transport for better design of molecular electronics. Here, the authors test two benchmark aromatic motifs and show how the coupling between π electrons and molecular vibration is affected by molecular edge topology.
Interatomic Coulombic decay (ICD) is a relaxation of an atom in a weakly bound environment by the transfer of excess energy to ionize the neighbouring atom. Here the authors observe intra-Rydberg ICD in neon clusters, which is a decay that involves the ionization of Rydberg atoms in the cluster.
X-ray photon correlation spectroscopy has been mainly used to measure slow dynamics using synchrotron sources. Here the authors demonstrate the split-and- delay pulse set-up to study nanosecond dynamics of gold nanoparticles using XPCS with free electron laser pulses.
The dynamics of liquid water is rich due to its complex, highly disordered hydrogen-bond network, which hasn’t been fully understood. Perakis et al. measure water dynamics at sub-100 fs and show that it cannot be described by simple thermal motion due to the build-up of tetrahedral structures upon supercooling.
Many photo-induced processes such as photosynthesis occur in organic molecules, but their femtosecond excited-state dynamics are difficult to track. Here, the authors exploit the element and site selectivity of soft X-ray absorption to sensitively follow the ultrafast ππ*/nπ* electronic relaxation of hetero-organic molecules.
Group IV–VI materials often exist in a state near an electronic or structural phase transition. Here, the authors use ultrafast X-ray scattering to show that coupling of band-edge electrons and phonons causes the ferroelectric instability observed in lead telluride.
Ultrafast nonadiabatic chemical dynamics during molecular photo-transformations remain challenging to describe since electronic/nuclear configurations are coupled. Here the authors use time-resolved X-ray absorption spectroscopy to probe the light-induced spin-state trapping dynamics of [Fe(bpy)3]2+beyond the Born-Oppenheimer approximation.
In BaFe2As2, the lattice couples strongly to the magnetic and electronic degrees of freedom, providing a way to control them. Here, by means of time-resolved X-ray scattering, the authors measure rapid lattice oscillations, which can induce changes in the material’s electronic and magnetic properties.
Designing catalysts and understanding the influence of ligands for particular transformations remains a highly challenging task. Here, the authors show that bisphosphine ligands can alter the geometry of the active site in silver catalysts, driving protonation and ultimately extrusion of carbon dioxide from formic acid.
Photoinduced electron transfer in solvated molecular assemblies occurs on the ultrafast timescale before full electronic and geometric relaxation take place. Here Canton et al.monitor this out-of-equilibrium process in a donor–acceptor bimetallic assembly using an X-ray free-electron laser.
Interactions between reactive excited states of molecular photocatalysts and surrounding solvent can dictate reaction pathways, but are not readily accessible to conventional spectroscopic methods. Here the authors use diffuse X-ray scattering and theory to study the atomistic solvation dynamics of a photoexcited di-iridium complex in acetonitrile.
The effect of dense plasma environment on the energy levels of an ion is usually described in terms of a lowering of its continuum level. Here the authors present an isochoric-heating experiment to measure and compare continuum lowering in single-species and mixture plasmas to provide insights for models.
Our understanding of shock metamorphism and thus the collision of planetary bodies is limited by a dependence on ex situ analyses. Here, the authors perform in situ analysis on shocked-produced densified glass and show that estimates of impactor size based on traditional techniques are likely inflated.