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Using single broadband X-ray pulses from a free-electron laser on a gaseous neon target, coherent, nonlinear four-photon interactions with core–shell electrons is demonstrated, representing a strategy for multidimensional correlation spectroscopy at the atomic scale.

X-ray photoelectron spectroscopy probes the chemical environment in a molecule at a specific atomic site. Here the authors extend this concept with a site selective trigger to follow chemical bond changes as they occur on the femtosecond time scale.

X-ray free electron lasers provide high photon flux to explore single particle diffraction imaging of biological samples. Here the authors present dynamic electronic structure calculations and benchmark them to single-particle XFEL diffraction data of sucrose clusters to predict optimal single-shot imaging conditions.

Since their initial operation, free-electron lasers are regularly upgraded in their performance and parameter control. Here the authors present the first lasing results of the soft X-ray free-electron laser beamline of the Paul Scherrer Institute, demonstrating different modes of operation and polarisation control of the tailored soft X-ray pulses.

A modern version of Newton's 'dusty 'mirror' experiment is made, whereby X-ray pulses are focused on a thin membrane with polystyrene particles placed in front of an X-ray mirror. After a pulse traverses through the sample, triggering the explosion of a particle, it is reflected back on to the sample by the mirror to probe this reaction. The resulting diffraction pattern contains accurate time and spatially resolved information about the exploding particles.

Lipidic sponge phase crystallization yields membrane protein microcrystals that can be injected into an X-ray free electron laser beam, yielding diffraction patterns that can be processed to recover the crystal structure.

Researchers describe a mechanism capable of compressing fast and intense X-ray pulses through the rapid loss of crystalline periodicity. It is hoped that this concept, combined with X-ray free-electron laser technology, will allow scientists to obtain structural information at atomic resolutions.

A femtosecond, high-intensity atomic X-ray laser with a photon energy of 849 electronvolts is produced in singly ionized neon by pumping using an X-ray free-electron laser.

Diffraction-before-destruction of ultrashort X-ray pulses can visualize non-equilibrium processes at the nanoscale with sub-femtosecond precision. Here, the authors demonstrate how the brightness and the spatial resolution of such snapshots can be substantially increased despite ionization.

Protein serial crystallography at X-ray free-electron lasers (XFELs) is a powerful technique for structure determination. Here, authors present a device for sample delivery designed to abate challenges to non-specialists allowing for compound screening.

Time-resolved measurements of the X-ray photoemission delay of core-level electrons using attosecond soft X-ray pulses from a free-electron laser can be used to determine the complex correlated dynamics of photoionization.

Expression of a protein in Sf9 insect cells at high concentration triggers formation of in vivo crystals that can be analyzed by serial femtosecond X-ray crystallography.

Researchers have demonstrated the generation and control of subfemtosecond pulse pairs from a two-colour X-ray free-electron laser and conducted pump–probe experiments in core-ionized molecules.

Proton migration in the acetylene cation is commonly used as a model to study isomerisation dynamics. Here, the authors use X-ray pump-probe experiments to study this process, and show that isomerization occurs significantly faster than expected—within the first 12 femtoseconds following core ionization.

The occurrence of thermodynamically metastable nanoparticles determines the particle growth in nature, but capturing them is experimentally challenging. Barke et al. identify the three-dimensional shape of metastable silver nanoparticles in gas phase, characterized by X-ray free-electron laser.

Imaging live cells at nanometre resolution is challenging because radiation damage kills the cells during exposure. Here, the authors overcome this difficulty in a ‘diffraction before destruction’ experiment using an X-ray laser and record signal to 4 nm resolution on a free-flying cell.

Availability of intense hard X-ray pulses allows exploration of multiple ionization effects in heavier elements. Here, the authors measure the complex charge state distributions of xenon and found a reasonable agreement by comparing with the model including the relativistic and resonance effects.

Researchers create high ionization states, up to Xe³⁶⁺, using 1.5 keV free-electron laser pulses. The higher than expected ionization may be due to transient resonance-enhanced absorption and the effect may play an important role in interactions of intense X-rays with high-Z elements and radiation damage.

70,000 diffraction patterns captured over twelve minutes at the Linac Coherent Light Source yield reconstructions of the smallest single biological objects imaged with an X-ray laser.

The start-up of the new femtosecond hard X-ray laser facility in Stanford, the Linac Coherent Light Source, has brought high expectations for a new era for biological imaging. The intense, ultrashort X-ray pulses allow diffraction imaging of small structures before radiation damage occurs. This new capability is tested for the problem of structure determination from nanocrystals of macromolecules that cannot be grown in large crystals. Over three million diffraction patterns were collected from a stream of nanocrystals of the membrane protein complex photosystem I, which allowed the assembly of a three-dimensional data set for this protein, and proves the concept of this imaging technique.

The start-up of the new femtosecond hard X-ray laser facility in Stanford, the Linac Coherent Light Source, has brought high expectations for a new era for biological imaging. The intense, ultrashort X-ray pulses allow diffraction imaging of small structures before radiation damage occurs. This new capability is tested for the problem of imaging a non-crystalline biological sample. Images of mimivirus are obtained, the largest known virus with a total diameter of about 0.75 micrometres, by injecting a beam of cooled mimivirus particles into the X-ray beam. The measurements indicate no damage during imaging and prove the concept of this imaging technique.

Single Xe clusters are superheated using an intense optical laser pulse and the structural evolution is imaged with a single X-ray pulse. Ultrafast surface softening on the nanometre scale is resolved within 100 fs at the vacuum/sample interface.

Femtosecond X-ray Fourier holography imaging with record-high lateral resolution below 20 nm is demonstrated. Phase information is encoded into the interference of the diffraction patterns of a reference particle with a measurement sample.