The US has unveiled a powerful new X-ray laser toolkit at SLAC’s Linac Coherent Light Source (LCLS), thanks to the transformative LCLS-II upgrade that boosts X-ray pulse rates by up to 10,000 times. This leap enables groundbreaking research into nature’s smallest mysteries, from quantum materials to molecular reactions. New instruments like qRIXS and chemRIXS use resonant inelastic X-ray scattering to reveal ultrafast dynamics in solids and liquids with unprecedented speed and clarity, turning days-long experiments into minutes. qRIXS, a massive 12-foot spectrometer, is now capturing detailed "movies" of energy flow in high-temperature superconductors, while chemRIXS analyzes delicate chemical processes in dilute solutions—key to understanding real-world reactions like photosynthesis. At the Time-resolved Atomic, Molecular and Optical Science (TMO) end station, instruments like the Multi-Resolution Cookie Box and the Dynamic REAction Microscope (DREAM) are revolutionizing how scientists observe electron dynamics and molecular explosions, allowing them to reconstruct molecular movies of chemical reactions in real time. These advances, fueled by a flood of data, are also accelerating AI-driven discovery, enabling smarter data analysis and real-time beamline optimization. With this new era of ultrafast, high-resolution science, researchers are unlocking answers to some of the most profound questions in physics, chemistry, and biology.

The U.S. has gained a powerful new toolkit for exploring nature’s smallest secrets, thanks to major upgrades at SLAC National Accelerator Laboratory’s Linac Coherent Light Source (LCLS). With the completion of the LCLS-II upgrade, the facility now delivers up to a million X-ray pulses per second—up from just 120—enabling scientists to study atomic and molecular processes with unprecedented speed and precision. This leap in performance has allowed SLAC researchers to reimagine and enhance a suite of advanced instruments, including qRIXS and chemRIXS, both based on resonant inelastic X-ray scattering (RIXS). This technique involves firing X-rays at a sample to excite electrons deep within atoms, then capturing the energy released as light. By analyzing this light, scientists can uncover detailed information about a material’s electronic structure and dynamic behavior. Georgi Dakovski, SLAC lead scientist and qRIXS instrument lead, explained that RIXS experiments were once extremely slow and inefficient—only a tiny fraction of X-ray photons reached the detector. With the new pulse rate, data collection that once took days now happens in minutes or seconds. “We can now watch energy flow through materials and see how atoms interact in real time,” Dakovski said. “We’re creating frame-by-frame movies of quantum processes.” The qRIXS instrument, a massive 12-foot spectrometer capable of swiveling 110 degrees, is now operational. Its ability to capture data from multiple angles with high resolution makes it ideal for studying quantum materials like high-temperature superconductors—materials that conduct electricity without resistance. Understanding their behavior could lead to breakthroughs in quantum computing, medical imaging, and ultra-efficient power transmission. Meanwhile, chemRIXS is transforming the study of chemical reactions in liquids. Previously limited to concentrated solutions, researchers can now analyze dilute samples that more closely mimic real-world conditions. Kristjan Kunnus, chemRIXS lead scientist, noted the upgrade has opened the door to studying processes like the intermediate steps of photosynthesis—key to developing artificial systems that mimic nature’s solar energy conversion. At the Time-resolved Atomic, Molecular and Optical Science (TMO) end station, new instruments are revealing the ultrafast dynamics of electrons in molecules. The Multi-Resolution Cookie Box (MRCO) uses 16 electron detectors arranged in a circle to capture the precise energy and direction of electrons ejected during reactions. This allows researchers to probe charge and energy transfer on timescales as short as a millionth of a billionth of a second—critical for understanding and improving catalysts and fuel systems. Another breakthrough is the Dynamic REAction Microscope, or DREAM. This instrument focuses X-rays on single molecules, stripping away electrons until the molecule explodes. Detectors capture the fragments, and by combining millions of these snapshots, scientists can reconstruct detailed images of chemical reactions in motion. James Cryan, TMO instrument lead, described it as a way to “watch how light triggers life’s processes—like sight, photosynthesis, and DNA’s response to radiation—at the most fundamental level.” In 2020, a prototype of DREAM took a week to collect data for a single frame. Now, with LCLS-II’s rapid pulse rate, researchers can gather enough data in hours to build full molecular movies. “This upgrade has turned the impossible into reality,” Cryan said. The massive data output from these experiments is also fueling the development of AI models that can help scientists analyze results faster, optimize beamline settings in real time, and discover new materials more efficiently. Matthias Kling, director of science and R&D at LCLS, emphasized that the integration of AI is reshaping the future of discovery. With these tools, researchers are no longer constrained by old limits. The upgraded LCLS is unlocking a new era of scientific exploration—where the invisible becomes visible, and the dynamics of life and matter unfold in real time.