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

Physics
Nikola

 An international group of researchers led by Ohio University Professor of Physics and Argonne National Laboratory scientist Saw Wai Hla has captured the first-ever X-ray SIGNAL (or SIGNATURE) of a single atom. This significant development may drastically alter how scientists identify the materials.

Since its discovery by Roentgen in 1895, X-rays have found widespread application in fields as diverse as medicine and airport security. Even NASA’s Mars rover, Curiosity, is outfitted with an X-ray instrument to analyse the Martian rock’s material composition. X-rays have crucial scientific applications, including material identification. Thanks to advancements in synchrotron X-ray sources and new technologies, the amount of sample material needed for X-ray detection has decreased dramatically over the years. Currently, the smallest sample size that can be X-rayed is an attogram, which is roughly 10,000 atoms or more. This is because the X-ray signal emitted by an atom is so weak that standard X-ray detectors cannot pick it up. Hla claims that his research group is finally making progress towards the long-held goal of X-raying a single atom.

Scanning probe microscopes can be used to take pictures of atoms, but X-rays are necessary to determine their composition. According to Hla, who also serves as the director of Ohio University’s Nanoscale and Quantum Phenomena Institute, “We can now detect exactly the type of a particular atom, one atom at a time, and can simultaneously measure its chemical state.” “Once we’ve accomplished it, we’ll be able to track the materials all the way down to the level of an individual atom. A potential cure or significant advancement in environmental and medical science could result from this. This is a finding that will change everything.

Hla and several other physicists and chemists, including PhD students at OHIO, used a purpose-built synchrotron X-ray instrument at the XTIP beamline of Advanced Photon Source and the Centre for Nanoscale Materials at Argonne National Laboratory. Their findings were published in Nature on May 31, 2023, and appeared on the cover of the print version of the journal on June 1, 2023.


The group decided to use iron and terbium atoms, each of which had been implanted into a different molecular host, as examples. The researchers used a technique called synchrotron X-ray scanning tunnelling microscopy (SX-STM), which involves positioning a sharp metal tip very close to the sample in order to collect X-ray excited electrons, in addition to conventional X-ray detectors. Photoabsorption of core-level electrons in SX-STM initiates X-ray spectroscopy, providing a powerful means of directly detecting the elemental type of the materials through elemental fingerprints.

Hla compares the spectra to fingerprints in that each one is distinct and can be used to identify a specific object.

Tolulope Michael Ajayi, the lead author of the publication and doing this work for his PhD thesis, said, “The technique used, and concept proven in this study, broke new ground in X-ray science and nanoscale studies.” Further, the ability to use X-rays to identify and characterise individual atoms has the potential to transform a wide range of disciplines and inspire the development of groundbreaking technologies, including quantum information and the detection of trace elements in environmental and medical studies. The development of cutting-edge tools for materials research has also been facilitated by this success.

Hla has worked alongside Advanced Photon Source at Argonne National Laboratory scientist Volker Rose over the past 12 years to build an SX-STM apparatus and associated measuring methodologies.
Over a period of 12 years, I supervised the PhD theses of four students at the University of Ohio working on SX-STM method development. Hla remarked, “We’ve come a long way to detect the X-ray signature of a single atom.”


Hla’s research is centred on nano and quantum sciences, with an emphasis on elucidating the atomic-level basis for the chemical and physical properties of materials. The primary objective of the team was to use this method to study the influence of its surroundings on a single rare-earth atom, in addition to achieving the X-ray signature of one atom.
Hla elaborated, “We have detected the chemical states of individual atoms.” According to the authors, “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 minerals are crucial to the development and improvement of technology since they are employed in commonplace gadgets like cell phones, computers, and televisions. This finding will allow scientists to better manage the atoms within diverse material hosts to fulfil the ever-changing needs of many fields by identifying not only the kind of element but also its chemical state. To identify the orientation of orbitals of a single molecule on a material surface with synchrotron X-rays, scientists have also created a novel technique dubbed “X-ray excited resonance tunnelling,” or X-ERT.
Hla added that their success “connects synchrotron X-rays with quantum tunnelling process to detect X-ray signature of an individual atom,” which would pave the way for future studies of the quantum and spin (magnetic) features of a single atom using synchrotron X-rays.
The research team also included Anh T. Ngo, currently an Associate Professor of Chemical Engineering at the University of Illinois at Chicago, and former OHIO graduate students Sanjoy Sarkar, Shaoze Wang, Kyaw Zin Latt, Tomas Rojas, and Anh T. Ngo, all of whom earned their Ph. D.s in Physics. Eric Masson, professor of chemistry and Roenigk chair in the College of Arts and Sciences, conceived and created the rare earth compound tested in this research.


Further revolutionising their applicability for use in gathering essential materials research and more, Hla and his research team will keep using X-rays to detect attributes of just one atom in the future.

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