Scientists x-ray individual atom for the first time

The breakthrough was achieved by a team from Ohio University, Argonne National Laboratory, the University of Illinois-Chicago and others, led by Ohio University professor of physics, and Argonne National Laboratory scientist, Saw Wai Hla.

Since their discovery in 1895, X-rays have been used extensively, from medical examinations to airport security screenings. Even Nasa’s Curiosity rover uses X-rays to study the material composition of rocks on the surface of Mars.

Over the years, the quantity of materials in a sample required for X-ray detection has been greatly reduced thanks to the development of synchrotron X-ray sources and new instruments.

But up to now, the smallest amount that can be X-rayed is an attogram, which is about 10,000 atoms or more. This is because the X-ray signal produced by an atom is extremely weak so it cannot be detected by conventional X-ray detectors.

“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,” explained research lead Saw Wai Hla.

“Once we are able to do that, we can trace the materials down to the 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.”

To test their theory, the team chose an iron atom and a terbium atom, both inserted in molecular hosts. To detect the X-ray signal of one atom, they supplemented conventional detectors in X-rays with a specialised detector made of a sharp metal tip positioned at extreme proximity to the sample to collect X-ray-excited electrons.

“The technique used, and concept proven in this study, broke new ground in X-ray science and nanoscale studies,” said Tolulope Michael Ajayi, first author of the paper.

“More so, using X-rays to detect and characterise individual atoms could revolutionise 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.”

In addition to achieving an X-ray signature of one atom, the team’s key goal was to use this technique to investigate the environmental effect on a single rare-earth atom.

“We have detected the chemical states of individual atoms as well,” Hla said. “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.”

Many rare-earth materials are used in everyday devices, such as cell phones, computers and televisions, to name a few, and are extremely important in creating and advancing technology.

Through this discovery, scientists can now identify not only the type of element but its chemical state, which will allow them to better manipulate the atoms inside different materials hosts.

The researchers plan to continue to use X-rays to detect properties of singular atoms and find ways to further their applications for use in gathering critical materials research.

The work was funded by the US Department of Energy, Office of Basic Energy Sciences.