New Imaging Technique Shows How Complex Molecules Buck and Twist

By Jamie Condliffe on at

It’s becoming gradually easier to see what molecules look like up close, but seeing how their shape changes in real-time is still incredibly hard. Now, a new technique allows scientists to see how molecules change their shape over the course just trillionths of a second.

Researchers from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg have built what they’re calling a molecular camera to see how atoms change position in a molecule in a matter of hundreds of femtoseconds. (For some context, a femtosecond is a millionth of a billionth of a second.)

Usually, imaging techniques used to capture the dynamics of molecules use two laser beams: a first ‘pulse’ to excite the molecule, a second ‘probe’ to acquire an image. But to get a fast exposure you need an incredibly bright pulse, which means the systems required become huge and prohibitively expensive. Instead, the team from Hamburg replaced the probe beam with electrons. The team explains why that’s useful:

Electrons have the advantage that they can directly image the positions of atoms in a molecule. As quantum particles, they have wave-like properties, just like light quanta. But their wavelengths are so short that they have no problem in detecting and imaging individual atoms even at low kinetic energy. They can be generated fairly easily in compact instruments.

In fact, the electron beam is able to capture an image of a molecular structure in a single shot, and the process can be repeated quickly to form a kind of film of how the molecule’s shape changes. In the GIF above, a new molecule known as Me4P[Pt(dmit)2]2 is imaged. Hit with laser light, it transforms from an electrical insulator to a metal — and the video, with 200 femtosecond between each frame, shows that happens because just a few of the atoms in the molecule shift around. The results are published in Science.

The team points out that the technique will allow researchers to quickly understand how dramatic changes in molecules results from subtle changes in their structure, something which has been virtually impossible in the past. “Thousands of possibilities are reduced to a few simple, basic dance steps of the atomic ballet,” in the words of Dwayne Miller, one of the researchers, in a press release. [Science via PhysOrg]

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