Less is more when measurinq atoms

摘要

If You want to look at individual atoms, it helps to have a powerful microscope. But for delicate situations such as a lone atom on the edge of a sheet of carbon atoms, a high-energy beam can disturb the bonds that hold such atoms in place, making them difficult to study. Now, for the first time, a low-energy beam has been used to count these bonds. In the past, beams of high-energy electrons have been used to probe individual atoms. For example, such an electron beam was used to identify single atoms of so-called "rare earth" elements that were trapped inside buckyballs, round cages made of carbon atoms. By looking at the energy spectra of the electrons that bounced back, researchers could deduce the size of the atom inside, and so identify it.