Scientists Finally Capture An X-Ray Of A Single Atom After Decades Of Effort

For more than a century, X-rays have helped scientists explore things that the human eye cannot see. Since Wilhelm Roentgen first discovered them in 1895, the technology has become one of the most powerful tools in science and medicine. Doctors use X-rays to diagnose broken bones and dental problems, airports use them to scan luggage, and researchers rely on them to understand the composition of materials. X-rays have even traveled beyond Earth, with NASA’s Curiosity rover carrying an X-ray instrument to analyze rocks on Mars. Despite their widespread use, there has always been a major limitation in how deeply X-rays could probe the building blocks of matter.

Until recently, scientists could not use X-rays to study a single atom. Even with advanced synchrotron facilities that generate extremely intense beams of X-rays, researchers still needed samples containing thousands of atoms to produce a detectable signal. That limitation has now been broken. A team of scientists led by Professor Saw Wai Hla from Ohio University and Argonne National Laboratory has successfully detected and analyzed the X-ray signature of a single atom for the first time. The breakthrough, described in the journal Nature, marks a major step forward in nanoscale science and could transform how researchers study materials, chemical reactions, and environmental processes at the most fundamental level.

Scientists report world’s first X-ray of a single atom in Nature.

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Why Detecting a Single Atom Was So Difficult

Scientists have long been able to image atoms using scanning probe microscopes. These powerful instruments can reveal the positions of atoms on a surface with extraordinary precision. However, imaging alone does not tell researchers what those atoms actually are. Without additional techniques, scientists cannot determine the chemical identity or state of the atom they are observing. X-rays provide that missing information because different elements produce unique spectral signatures when exposed to X-ray radiation.

The challenge is that the X-ray signal from a single atom is incredibly weak. For decades, even the most sophisticated X-ray detectors required a relatively large number of atoms in a sample before a reliable signal could be measured. Researchers managed to reduce this requirement over time through improvements in synchrotron X-ray sources and instrumentation, but there was still a fundamental barrier. Until now, the smallest quantity scientists could analyze was roughly an attogram of material, which corresponds to about ten thousand atoms.

Because of this limitation, detecting the X-ray signature of just one atom became a long standing goal in the scientific community. Achieving it required not only stronger X-ray sources but also entirely new ways of capturing the tiny signals produced when X-rays interact with matter. Researchers needed a method sensitive enough to detect the electrons released by a single atom after it absorbed X-ray energy.

Professor Saw Wai Hla summarized the importance of overcoming this challenge by explaining, “Atoms can be routinely imaged with scanning probe microscopes, but without X-rays one cannot tell what they are made of. We can now detect exactly the type of a particular atom, one atom-at-a-time, and can simultaneously measure its chemical state.”

The Technology That Made It Possible

To reach this milestone, the research team developed a specialized technique called synchrotron X-ray scanning tunneling microscopy, often abbreviated as SX-STM. The experiments were performed using a purpose-built synchrotron X-ray instrument at the XTIP beamline of the Advanced Photon Source and the Center for Nanoscale Materials at Argonne National Laboratory. These facilities generate extremely intense beams of X-rays that can interact with matter at the atomic scale.

Instead of relying solely on conventional X-ray detectors, the researchers added a highly sensitive detector made from a sharp metal tip. This tip was positioned extremely close to the sample being studied. When the X-rays struck the atom, they excited core level electrons within that atom. The excited electrons then tunneled toward the nearby detector tip, producing a measurable signal.

This approach allowed scientists to collect what they describe as an elemental fingerprint. Each element produces a unique spectral pattern when its electrons absorb X-ray energy. By analyzing these spectra, researchers can determine exactly which element they are observing and gain insight into its chemical environment.

The team also developed a related method known as X-ray excited resonance tunneling, or X-ERT. This technique connects synchrotron X-ray excitation with quantum tunneling processes, allowing scientists to detect extremely small signals that were previously impossible to measure. According to the researchers, this new method opens entirely new possibilities for studying atoms and molecules at the nanoscale.

The Atoms That Proved the Concept

To demonstrate their technique, the researchers selected two different types of atoms for study. The first was iron, a common element that plays an important role in many chemical and biological processes. The second was terbium, a rare earth metal widely used in modern technology such as electronics, displays, and magnetic devices.

Each atom was placed inside a carefully designed molecular host structure that stabilized it during the experiment. By directing synchrotron X-rays onto these structures and using the SX-STM detector, the scientists successfully measured the X-ray signal produced by each individual atom. This confirmed that the method could identify single atoms based on their unique spectral fingerprints.

The experiments also revealed differences in how the atoms behaved chemically within their environments. According to the research team, the terbium atom remained relatively isolated and stable inside its molecular host, while the iron atom showed strong interaction with surrounding atoms.

Hla described this observation by saying, “We have detected the chemical states of individual atoms as well. By comparing the chemical states of an iron atom and a terbium atom inside respective molecular hosts, we find that the terbium atom, a rare-earth metal, is rather isolated and does not change its chemical state while the iron atom strongly interacts with its surrounding.”

Why This Discovery Matters For Science

Although detecting a single atom may sound like a purely technical achievement, the implications are far reaching. Being able to identify and study individual atoms provides scientists with an unprecedented level of detail about how materials behave. Many properties of materials such as strength, conductivity, and chemical reactivity are determined by interactions that occur at the atomic level.

With this new technique, researchers can examine those interactions with far greater precision than before. Instead of studying the average behavior of large groups of atoms, scientists can now investigate how individual atoms interact with their surroundings. This capability could lead to deeper insights into the design of advanced materials for electronics, energy storage, and other technologies.

Environmental science may also benefit from this breakthrough. Many pollutants and trace elements exist in extremely small quantities that are difficult to detect with conventional instruments. The ability to identify individual atoms could help scientists track contaminants more accurately and understand how they interact with ecosystems and living organisms.

Medical research could also gain new tools from this discovery. Understanding chemical reactions at the atomic level may improve the development of drugs and diagnostic technologies. By observing how atoms behave inside complex molecular systems, scientists may uncover new ways to target diseases or improve treatments.

A Breakthrough Years In The Making

Although the results were recently published, the technology behind the discovery was developed over many years. Professor Hla and his collaborators spent more than a decade refining the instruments and measurement techniques required to detect such tiny signals. The effort involved scientists, engineers, and graduate students working together across several institutions.

The project included contributions from Ohio University, Argonne National Laboratory, and the University of Illinois Chicago. Graduate students played a particularly important role in advancing the research, helping to design experiments and develop the methods used to interpret the data. According to the team, several PhD projects over a twelve-year period focused on building and improving the SX-STM technique.

Tolulope Michael Ajayi, the first author of the study, conducted much of the research as part of his doctoral work. Reflecting on the significance of the achievement, Ajayi said, “The technique used, and concept proven in this study, broke new ground in X-ray science and nanoscale studies. More so, using X-rays to detect and characterize individual atoms could revolutionize research and give birth to new technologies in areas such as quantum information and the detection of trace elements in environmental and medical research, to name a few. This achievement also opens the road for advanced materials science instrumentation.”

The study ultimately appeared in Nature and even featured on the cover of the journal’s print edition, highlighting its importance for the scientific community.

The Future Of Atomic Level Research

Now that researchers have successfully captured the X-ray signature of a single atom, the next step is to expand the technique and apply it to more complex scientific questions. Scientists hope to use the method to explore quantum properties of individual atoms, including magnetic behavior and electron spin. These properties are essential for emerging technologies such as quantum computing and advanced nanodevices.

Rare earth elements like terbium are especially important for modern electronics. They are used in devices such as smartphones, computers, televisions, and advanced magnets. By studying these elements at the level of individual atoms, researchers may gain insights that help improve the performance and efficiency of future technologies.

The ability to examine atomic fingerprints may also help scientists design materials with specific properties. Instead of discovering materials through trial and error, researchers could analyze how individual atoms behave and engineer materials from the bottom up. This approach could accelerate innovation in fields ranging from renewable energy to next generation electronics.

Professor Hla emphasized the broader impact of the breakthrough by stating, “Once we are able to do that, we can trace the materials down to ultimate limit of just one atom. This will have a great impact on environmental and medical sciences and maybe even find a cure that can have a huge impact for humankind. This discovery will transform the world.”

Looking At The Smallest Building Blocks

The ability to detect the X-ray signal of a single atom represents a remarkable step forward in scientific capability. For the first time, researchers can combine the chemical sensitivity of X-rays with the spatial precision needed to study individual atoms. This combination allows scientists to explore the fundamental structure of matter with unprecedented detail.

What makes the achievement especially exciting is that it opens the door to entirely new kinds of experiments. Instead of studying large collections of atoms, scientists can now investigate the behavior of matter one atom at a time. This approach may reveal new insights about how chemical reactions occur, how materials form, and how atomic interactions influence the world around us.

Scientific breakthroughs often begin with tools that allow researchers to see something they could not see before. The detection of a single atom using X-rays may become one of those transformative tools, giving scientists a clearer view of the microscopic processes that shape technology, medicine, and the environment.

Sometimes the most powerful discoveries come from observing the smallest parts of nature. In this case, one tiny atomic signal may lead to a much bigger understanding of the universe.

Sources:

1. Ajayi, T. M., Shirato, N., Rojas, T., Wieghold, S., Cheng, X., Latt, K. Z., Trainer, D. J., Dandu, N. K., Li, Y., Premarathna, S., Sarkar, S., Rosenmann, D., Liu, Y., Kyritsakas, N., Wang, S., Masson, E., Rose, V., Li, X., Ngo, A. T., & Hla, S. (2023). Characterization of just one atom using synchrotron X-rays. Nature, 618(7963), 69–73. https://doi.org/10.1038/s41586-023-06011-w
2. Scientists report world’s first X-ray of a single atom in Nature. (2025, April 2). OHIO Today. https://www.ohio.edu/news/2023/05/scientists-report-worlds-first-x-ray-single-atom-nature
3. [Wilhelm Conrad Röntgen and the discovery of X-rays]. (1996, January 1). PubMed. https://pubmed.ncbi.nlm.nih.gov/8696882/