Science: An advance in imaging single atoms

An article in ars Technica describes an improvement in single atom imaging. In 2013, when dinosaurs still roamed the Earth, a newly developed quantum microscope was able to look inside a hydrogen atom to visualize its electron orbital or density cloud. That was pretty cool.

Now, an X-ray microscope has been developed that allows detection of what kind of atom is there and measurement of its chemical state. In this instance, an iron atom with the chemical symbol Fe is visualized when nestled inside a larger molecular structure. The image detector is shown as the tip and the X-rays shining on the Fe atom shown in red. 

 

The image shows the Fe atom in center of the ring-like molecular structure it is setting in.

ars Technica comments:

Physicists can now routinely image atoms with scanning-probe microscopes. These work by running a very sharp tip over a surface and forming the image of the surface from a signal read from the tip—akin to a record player reading the grooves on a record to play sound. The first of these techniques, scanning tunneling microscopy (STM), was developed by IBM researchers in 1981. STM relies on quantum mechanical tunneling effects. As the microscope's tip is scanned over a surface, electrons tunnel from the tip into the surface. The tunneling current is measured and can be transformed into an image. (Fun fact: In 1989, IBM researchers used STM to spell out "IBM" using 35 xenon atoms on a nickel substrate.)

Hla has been working for the last 12 years to develop an X-ray version of STM: synchrotron X-ray-scanning tunneling microscopy, or SX-STM, which would enable scientists to identify the type of atom and its chemical state. X-ray imaging methods like synchrotron radiation are widely used across myriad disciplines, including art and archaeology. But the smallest amount to date that can be X-rayed is an attogram, or roughly 10,000 atoms. That's because the X-ray emission of a single atom is just too weak to be detected—until now.

SX-STM combines conventional synchrotron radiation with quantum tunneling. It replaces the conventional X-ray detector used in most synchrotron radiation experiments with a different kind of detector: a sharp metal tip placed extremely close to the sample, the better to collect electrons pushed into an excited state by the X-rays.

There's just nothing like excited electrons to give away the secrets of little things. The researchers believe that the short-term implications for this will be in the medical and environmental sciences and then spread from there.

By Germaine: The excited electron 

Unexcited Germaine on the left

Excited Germaine on the right