Light, Materials, News

An atom observed by X-rays

For the first time, a single atom received a X-rays beam, identifying the elemente and revealing information about the chemical state.

Source: Sci News

“Atoms can be routinely imaged with scanning probe microscopes, but without X-rays one cannot tell what they are made of,” said Dr. Hla, who is also the director of the Nanoscale and Quantum Phenomena Institute at Ohio University.

“We can now detect exactly the type of a particular atom, one atom-at-a-time, and can simultaneously measure its chemical state.”

Dr. Hla and co-authors conducted their experiment at the XTIP beamline at the Advanced Photon Source and the Center for Nanoscale Materials at Argonne National Laboratory.

For demonstration, they chose an iron atom and a terbium atom, both inserted in respective molecular hosts.

X-rays in an iron atom.
When X-rays hit the iron atom (Fe), electron gain energy, due to photoelectric effect, and go to detector’s tip. Revealing the element and atom’s chemical state. Image is from the same news source.

To detect X-ray signal of one atom, they used a technique known as synchrotron X-ray scanning tunneling microscopy (SX-STM).

“The capabilities of synchrotron light sources have been continuously upgraded to improve resolution and minimum sample quantity required for measurements.”, according to the team.

“So far, an attogram amount of sample can be detected by X-rays. However, it is still in the range of over 10,000 atoms and obtaining much smaller sample is becoming extremely arduous.”

1 attogram is equal to 1\cdot 10^{-18} gram. Much smaller than nanoscale, which is 1\cdot 10^{-9}.

“If X-rays could be used to detect just one atom, it would further revolutionize their applications to an unprecedented level, from quantum information technology to environmental and medical research.”

“One way to overcome these challenges is to supplant conventional detectors with a specialized detector made of a sharp metal tip positioned at extreme proximity to the sample to collect X-ray-excited electrons.

molecules saw by X-rays.
On the left, ring-shaped molecule’s image, where there’s an iron atom. On the right, This atom’s X-ray signature. Image is from the same news source.

X-ray spectroscopy in SX-STM is triggered by photoabsorption of core level electrons, which constitutes elemental fingerprints and is effective in identifying the elemental type of the 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.”, added Tolulope Michael Ajayi, also from Argonne National Laboratory and Ohio University.

In addition to achieving 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.

“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.”, said Dr. Hla.

About Pedro Ney Stroski

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