Data Systems

Atomic, molecular, and optical science: By inducing energy modulations in the LCLS electron beam, high-current spikes could be produced in a magnetic chicane, which upon injection into an undulator led to the generation of widely tunable attosecond pulses with an intensity sufficient to drive nonlinear processes. The attosecond pulses generated at LCLS enable attosecond pump- attosecond probe experiments, as well as experiments where core-shell electrons are used to observe electron dynamics from the viewpoint of a particular atom. These attosecond capabilities recently led to a first major scientific result, namely the observation of coherent electron motion during Auger-Meitner decay and should lead to a deeper understanding of the role of electron correlation in quantum materials. 

Biological science: LCLS experiments have revealed exquisite detail of ligand binding to several challenging membrane proteins by the use of the serial femtosecond crystallography method, which was developed to capture diffraction of protein crystals from single sample-destroying LCLS pulses. The LCLS has engendered a major advance in the understanding of important enzyme-catalyzed reactions. Using LCLS, short-lived intermediates and transient states of enzyme reactions are simultaneously characterized spectroscopically and “seen” in crystal structures. Further, the femtosecond time scale of LCLS pulses is highly relevant to chemical reactions. Data on the spectroscopic and structural properties of intermediates substantially advance reaction theory and our ability to simulate reaction trajectories in other enzyme systems. 

Condensed-phase chemistry and catalysis: Experiments at LCLS have changed the way the scientific community thinks about molecules. Seminal and paradigm-shifting discoveries were enabled by the unique capabilities to probe the electronic and geometric properties of molecules and chemical systems at a more fundamental level than was ever possible before. Completely new observables were revealed, and the field was pushed beyond the boundaries of what is currently known and/or presumed to be true. This created new paradigms for chemical transformations. The fundamental new knowledge and the new approaches provide templates for probing a broad array of reactions spanning chemical, biological, and materials chemistries for new ways of translating the fundamental understanding of chemical systems to solutions of key challenges for a sustainable future. 

Gas-phase chemistry: LCLS experiments provide the long sought-after separation of structural and electronic effects, allowing the extraction of molecular dynamics directly from the experimental results. The pioneering experimental capabilities at LCLS include: 1) the ability to record time-resolved X-ray diffraction using the free-electron laser and time-resolved electron diffraction through the Ultrafast Electron Diffraction (UED) instrument; 2) the ability to implement spectroscopic techniques based on site-specific core-level photoabsorption. The UED instrument enabled the study of ring opening of cyclohexadiene with unprecedented sub- ängstrom spatial and femtosecond temporal resolution. The X-ray wavelength of the LCLS allows the development of measurement schemes that are based on diffraction, which are ideally suited for measuring time-dependent structural changes, as well as the development of novel techniques that are uniquely sensitive to time-dependent electronic changes in a molecule, and moreover, from the viewpoint of a particular atom within the molecule. 

Materials science and condensed matter physics: LCLS, with complementary advances in theory, simulation, and materials synthesis, has vastly expanded the range of materials phenomena that the materials community can study and ultimately control. Discoveries at LCLS have initiated the coherent control of excitations in a previously inaccessible regime in which it is possible to use light and other experimental tools to interact directly with the relevant physical phenomena. Atomic-scale information derived from X-ray scattering studies at LCLS has provided an understanding of the transformations of materials between phases, specifically in highly disordered systems for which the dynamics at short time scales have been previously unknown. LCLS has also provided new insights into energetically fragile many-electron dynamics of quantum materials via the separation of coupled dynamics in the time domain, based on its unique combination of selective near-equilibrium perturbation of coupled modes with precision snapshots of the electronic and atomic structure at fundamental length and time scales. Novel techniques and methods pioneered at LCLS will continue to offer new insight into the structure and excited states of solids and nanoscale materials. 

Materials in extreme conditions: Experiments at LCLS have provided unique insight into strength and plasticity at the lattice level, enabling links to macroscopic models that bridge micro- to macro-length scales in an area of importance to national security. The Matter in Extreme Conditions (MEC) platform at LCLS has provided completely new insights into pressure induced phase transitions at ultrahigh rates, demonstrating, for example, that the most complex phase a single element can form (an incommensurate host-guest structure) develops in less than a nanosecond. Complex physics that may take place in planetary physics – for example the properties of hydrocarbons in large planets – is being explored with LCLS. Finally, the ability of LCLS to create uniform hot (multi-million Kelvin) plasmas at exactly solid density is providing completely a new understanding of dense quantum plasmas.