Electron microscopes have given scientists unprecedented views of atomic and molecular structures. Now those vistas are evolving from still photographs into motion pictures. Physicist Ahmed Zewail of Caltech, who won the 1999 Nobel Prize in Chemistry for his use of lasers to study chemical reactions, is pioneering 4-D electron microscopy, which allows direct observation of atomic-scale changes in real time. His filmmaking technique relies on applying a short laser pulse to the subject, followed by an ultrafast pulse of electrons, which scatter off the material to produce an image for the microscope. A series of these images can be collected in rapid succession and viewed as a movie. The extremely brief electron pulses ensure that the image remains sharp, much like a short-exposure photograph of a speeding object.
In late 2008 Zewail and his colleagues announced that they had observed atomic motion in gold and in graphite (a sheet of carbon atoms). They discovered that atoms in heated graphite began to pulse in an unexpected synchronized “drumming” action, much like a heartbeat. Last summer the lab reported capturing changes in the pattern of bonding among graphite’s carbon atoms following intense compression of the sample. And in December they described watching nanotubes briefly glow after being hit with laser light. “You can see things evolve over time in a way that you never could with a snapshot,” says physicist and collaborator Brett Barwick. Eventually the group hopes to study chemical reactions in living cells.