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The attomicroscope is a variant of the transmission electron microscope that uses a beam of electrons to image objects a few nanometers in diameter (SN: July 16, 2008). Like light, electrons can be thought of as waves; however, their wavelengths are much smaller than those of light. This means that electron beams have better resolution than traditional lasers and can detect much smaller objects, such as atoms and other clouds of electrons.
To obtain the ultrafast images, Hassan and his colleagues used a laser to split the electron beam into ultrashort pulses. Like a camera shutter, these pulses allowed them to take a new picture of the electrons in the graphene sheet every 625 attoseconds — roughly 1,000 times faster than existing techniques.
Selected attomicroscope images taken at intervals of about 1,200 attoseconds show how electrons move through graphene under laser irradiation. The small black dots represent carbon atoms. Red areas have high electron density, while white and blue areas have low electron density compared to graphene without laser irradiation. Mohammed Hassan
The microscope can't yet capture images of single electrons, because that requires extremely high spatial resolution, but by stitching together the images they collected, the scientists created a kind of stop-motion movie that shows how clusters of electrons move through the molecule.
The technique could enable researchers to see how chemical reactions happen or examine how electrons move through DNA, Hassan said — information that could help scientists develop new materials and personalized medicines.
“With this new tool, we're trying to build a bridge between what scientists discover in the lab and real-world applications that could impact our daily lives,” he says.
