X-ray of a single atom captured

 Breakthrough : Scientists captured the world's first ever X-ray of a single atom         

In a remarkable feat, a team of scientists has taken the world’s first X-ray signature of just one atom. This stunning achievement could revolutionize the way scientists detect materials. The research team was led by Saw Wai Hla, Professor of Physics at Ohio University and scientist at Argonne National Laboratory. Scientists have now achieved what was once considered to be almost unattainable: X-raying a single atom. This extraordinary accomplishment was made possible by an international team of researchers.

For over a century, X-ray technology has been instrumental in various fields. Since its discovery by Roentgen in 1895, X-rays have been used in various applications, from medical examinations to security screenings in airports. Even NASA’s Mars rover, Curiosity, is equipped with an X-ray device to examine the materials composition of rocks on Mars. Over the years, advancements in synchrotron X-ray sources and new instruments have greatly reduced the quantity of materials required for X-ray detection. However, until now, the smallest amount one could X-ray a sample was in attogram, which is about 10,000 atoms or more. This limitation was due to the extremely weak X-ray signal produced by an atom, making it undetectable by conventional X-ray detectors. The main use of X-rays in the scientific world is in determining the type of materials present in a given sample. However, the minimum quantity of material required for X-ray detection has been considerably reduced thanks to the advent of synchrotron X-ray sources and innovative instruments. 

Previously, the smallest amount one could X-ray was an attogram, which equates to approximately 10,000 atoms or more. This limitation was due to the extraordinarily faint X-ray signal emitted by an individual atom, too weak to be detected by traditional X-ray detectors. This ambitious goal of X-raying a single atom has now been achieved by Professor Hla's team, fulfilling a long-held dream of the scientific community. According to Hla, it has been a long-standing dream of scientists to X-ray just one atom, which is now being realized by his research team. “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 Hla, who is also the director of the Nanoscale and Quantum Phenomena Institute at Ohio University. “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,” Hla continued.

Published in the renowned scientific journal Nature, their study outlined how this ground breaking feat was achieved. The research was conducted using a specially designed synchrotron X-ray instrument located at the XTIP beamline of the Advanced Photon Source and the Centre for Nanoscale Materials at Argonne National Laboratory. They chose an iron atom and a terbium atom, both inserted in respective molecular hosts, for demonstration. To detect the X-ray signal of one atom, the team supplemented conventional detectors in X-rays with a specialized detector made of a sharp metal tip positioned at extreme proximity to the sample to collect X-ray excited electrons. This is a technique known as synchrotron X-ray scanning tunneling microscopy or SX-STM. “The technique used, and concept proven in this study, broke new ground in X-ray science and nanoscale studies,” said Tolulope Michael Ajayi, the first author of the paper and a Ph.D. student working on this project as part of his thesis.

This method, called synchrotron X-ray scanning tunneling microscopy (SX-STM), enabled the collection of X-ray excited electrons. This innovative technique allows for the identification of the elemental type of materials directly. “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,” Ajayi concluded. Supramolecular assemblies of six rubidium and one iron atom. Scanning tunneling microscopy revealed the clear signal of the one iron atom.

Over the past 12 years, Hla has been intricately involved in the development of the SX-STM instrument and its measurement methods alongside Volker Rose, a scientist at the Advanced Photon Source at Argonne National Laboratory. “I have been able to successfully supervise four OHIO graduate students for their Ph.D. theses related to SX-STM method development over a 12-year period. We have come a long way to achieve the detection of a single atom X-ray signature,” Hla said. When X-rays (blue colour) illuminate onto an iron atom (red ball at the centre of the molecule), core level electrons are excited. X-ray excited electrons are then tunnel to the detector tip (grey) via overlapping atomic/molecular orbitals, which provide elemental and chemical information of the iron atom. 

This study is a giant leap forward in the field of nano and quantum sciences, focusing on understanding the chemical and physical properties of materials at the fundamental level - on an individual atom basis. Through this discovery, scientists can now not only identify the elemental type of an atom but also its chemical state, potentially revolutionizing the field of material science. In addition to achieving the 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 explained. “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.” Rare-earth materials are extremely important in creating and advancing technology, and are used in everyday devices such as cell phones, computers, and televisions. Through this discovery, scientists can now identify not only the type of element but its chemical state as well, allowing them to better manipulate atoms inside different materials hosts to meet ever-changing needs in various fields.

Moreover, the research team has also developed a new method called “X-ray excited resonance tunneling or X-ERT” that allows them to detect how orbitals of a single molecule orient on a material surface using synchrotron X-rays. “This achievement connects synchrotron X-rays with quantum tunneling process to detect X-ray signature of an individual atom and opens many exciting research directions including the research on quantum and spin (magnetic) properties of just one atom using synchrotron X-rays,” Hla excitedly concluded. Professor Hla and his team of researchers are committed to further exploring the potential of this breakthrough discovery. Their aim is to continue to use X-rays to detect properties of single atoms, aiming to revolutionize applications for material research and beyond. Their research could very well redefine our understanding of the atomic world, leading to unprecedented developments in science and technology. This landmark achievement in X-ray technology heralds an exciting new era in scientific research.

In conclusion, the incredible feat of capturing the first-ever X-ray signature of a single atom marks a significant milestone in the field of X-ray science and nanoscale studies. This achievement, made possible by the dedicated efforts of a collaborative research team led by Professor Saw Wai Hla, opens up a world of possibilities for scientific research and technological advancements. By pushing the boundaries of what was previously thought to be undetectable, this innovative technique has the potential to revolutionize various fields, from environmental and medical sciences to quantum information and advanced materials science instrumentation. As scientists continue to explore the capabilities of this powerful tool, they pave the way for discoveries that could have a profound impact on our understanding of the world at the atomic level and beyond. As Professor Hla concluded, "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."