Attempts at atom imaging began in the 1950s and advanced in 2008 to image a single hydrogen atom. Now, at long last, we have the first X-ray of a single atom, courtesy of scientists from Ohio University and Argonne National Laboratory, according to a new paper published in the journal Nature.

Co-author Saw-Wai Hla, a physicist at Ohio University and Argonne National Laboratory said: “We can now detect exactly the type of a particular atom, one atom at a time, and can simultaneously measure its chemical state. This will have a great impact on environmental and medical sciences.”

To image inside an atom, lead researcher Tolulope Ajayi and his colleagues used a technique that combines synchrotron (fine-tuned high-energy) X-rays with a microscopy technique for atomic-scale imaging called scanning tunneling microscopy. This employs a sharp-tipped probe a few atoms wide that interacts with the electrons of test material. It uses “quantum tunneling”, causing an electric current to flow into the microscope depending on what the tip sees.

At very close range, say under a billionth of a meter, the precise position of an electron is uncertain, smearing it across the space between the material and the probe. This is because of quantum mechanics. The state of the atom and its electrons can be measured in the resulting current from the moving electron. The combined technique is called synchrotron X-ray scanning tunneling microscopy (SX-STM).

First they created supramolecular assemblies, including 1 iron atom, 6 rubidium atoms and a complex ring of carbon and other atoms. Then the team used the SX-STM to study the a single iron atom, and make the x-ray.

The practical uses come from the ever-more complex materials used in modern electronics, that can now be adjusted on the atomic level, detecting trace elements and chemicals, even in archeology.