Kim’s RIXS Technique Probes Electron Dynamics for New Discoveries

At the Department of Energy’s Argonne National Laboratory, physicist Jung Ho Kim is leveraging resonant inelastic X-ray scattering (RIXS) to unlock the secrets of material behavior at the atomic level. Working at the Advanced Photon Source (APS), a national facility, Kim measures minuscule changes in particles to understand the fundamental properties of metals and other materials, with applications spanning superconductivity to quantum computing. “Ultimately, my goal is to help scientists figure out why their material behaves the way it does,” he said, emphasizing the technique’s role in driving innovation. Kim’s dedication to RIXS builds upon early work with photoemission spectroscopy at Seoul National University, a focus sparked by a lifelong curiosity; he explained, “I’ve always been interested in understanding how things work,” recalling a student’s path shaped by a rapidly changing South Korea. Resonant Inelastic X-ray Scattering (RIXS) Technique Explained Physicist Jung Ho Kim has dedicated his career to refining resonant inelastic X-ray scattering, or RIXS, a spectroscopic tool increasingly vital for materials science and quantum research. The APS, a key DOE Office of Science user facility, provides the intense X-ray beams necessary for this work; Kim stated that “Without it, I couldn’t have done my research,” emphasizing the facility’s crucial role. RIXS functions by detecting and studying how groups of particles move and interact, providing insights into a material’s lattice vibrations, charge movement, spin behavior, and electron orbital configurations. The recent APS Upgrade (APS-U) project has further enhanced RIXS capabilities at Sector 27, the beamline Kim oversees, making measurements faster and more robust. This improvement is critical as researchers push the boundaries of quantum science and require increasingly precise experimental tools. “My goal is to keep pushing the capabilities of RIXS so that it remains one of the most powerful tools for scientific discovery,” Kim said, outlining his commitment to innovation. He continued, “Whether that means improving energy resolution, reducing beam size, accelerating measurements, or inventing new measurement modes, the aim is to let users see the electron, spin, and orbital dynamics that tomorrow’s science will demand.” Sector 27 & The APS Upgrade Enhance RIXS Capabilities Sector 27 at the Argonne National Laboratory’s Advanced Photon Source (APS) is a premier global facility for resonant inelastic X-ray scattering (RIXS) research, continually refined to meet the evolving demands of materials science and quantum physics. Following the completion of the APS Upgrade (APS-U) project, Sector 27 was the first beamline to come back online, immediately capitalizing on the facility’s brighter X-ray beams. This prioritization underscores the importance of RIXS as a core capability for Argonne, allowing for faster and more reliable measurements at the mega-electron volt energy resolution level. Kim’s dedication to RIXS stems from a long-held fascination with understanding fundamental principles, a curiosity that began during his undergraduate studies at Seoul National University where he first explored photoemission spectroscopy. He explained, “When a new idea pops into my head, we can usually try it out the same week, sometimes the same day,” highlighting the collaborative environment and readily available resources that accelerate scientific progress. This responsiveness allows the team to quickly translate successful experiments into new capabilities accessible to the wider research community, solidifying Sector 27’s position as a leading RIXS facility and a vital resource for unraveling the complexities of materials at the atomic level. My goal is to keep pushing the capabilities of RIXS so that it remains one of the most powerful tools for scientific discovery. Jung Ho Kim, physicist at the APS From Photoemission Spectroscopy to Observing Collective Spin Excitations Photoemission spectroscopy, which involves illuminating a sample with X-rays and analyzing the emitted electrons, allowed him to map a material’s electronic landscape, controlling properties such as conductivity, magnetism, and superconductivity. This early work proved crucial when Kim transitioned to resonant inelastic X-ray scattering (RIXS) during postdoctoral research at the University of Toronto. Recognizing its potential, he saw RIXS as a tool to reveal how particles move and interact within materials, going beyond the capabilities of his initial spectroscopic studies. He joined Argonne in 2008, drawn by the fact that “The APS had the only hard X-ray RIXS facility in the United States,” a necessity for his research. Shortly after arriving, Kim led a project that demonstrated RIXS could detect collective spin excitations, previously studied with neutron scattering, establishing a new capability for the technique. “We remain the leading RIXS facility in the world,” he stated, emphasizing the facility’s continued prominence. My goal is to keep pushing the capabilities of RIXS so that it remains one of the most powerful tools for scientific discovery. Whether that means improving energy resolution, reducing beam size, accelerating measurements or inventing new measurement modes, the aim is to let users see the electron, spin and orbital dynamics that tomorrow’s science will demand – today. Source: https://www.aps.anl.gov/APS-News/2026-04-21/jung-ho-kim-is-making-quantum-visible-at-the-advanced-photon-source/2026-04-21 ADIABATIC QUANTUM COMPUTING ANGLE-RESOLVED PHOTOEMISSION SPECTROSCOPY ARGONNE NATIONAL LABORATORY RIXS SUPERCONDUCTIVITY Ivy Delaney We've seen the rise of AI over the last few short years with the rise of the LLM and companies such as Open AI with its ChatGPT service. Ivy has been working with Neural Networks, Machine Learning and AI since the mid nineties and talk about the latest exciting developments in the field. 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