Berkeley Lab develops ultrafast electron-firing device to observe chemical reactions

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The Lawrence Berkeley National Laboratory has developed an ultrafast electron-firing instrument that will allow scientists to observe rapid chemical processes at the atomic scale.

The High Repetition-rate Electron Scattering apparatus, or HiRes, was spearheaded by Berkeley Lab scientist Daniele Filippetto and was funded for the past five years in part by the U.S. Department of Energy’s Early Careers Research program. After delivering its first electron beam in March, scientists are poised to use it for the first time in experiments next month.

According to Filippetto, similar electron instruments currently exist in Europe and parts of the United States, but what makes HiRes unique is its ability to produce a high flux of electrons per second.

“We can make movies of molecules bonding or breaking the bonds,” Filippetto said. “These can only be done if you have a very short electron process — your camera must be very fast.”

Because the camera’s shutter must move quickly to capture the rapid motion, the apparatus must produce a great deal of electrons — like light in a camera — in order for the visualization to be clear.

HiRes can stream electrons at a rate of 1 trillion electrons per second, according to a Berkeley Lab press release.

There are three steps to analyzing a sample with the apparatus, according to Filippetto. The first step involves the utilization of short but intense laser beams to heat a material to extract electron bunches.

Then, the cloud of electrons is accelerated through the use of oscillating radio frequency fields. This acceleration is vital for the electrons to gain sufficient energy to overcome repelling forces between each other.

In the final step, the electrons drift through a tube in a vacuum and are focused through magnetic fields, eventually heating the sample. Using the electrons with the assistance of a pump — usually in the form of a laser — scientists are then able to capture a pattern that models the reaction.

Andrew Minor, campus professor of materials science and engineering and leader of the Minor Research Group, is optimistic about the impact of HiRes on future research. Minor, who is collaborating with Filippetto on the first experiment using HiRes, said the apparatus will lead to more thorough comprehension of ultrafast processes.

“Before this, we could only look at things in real-time,” Minor said. “Oftentimes, what’s most important is looking at things in a nanosecond time scale.”

Next month, Filippetto will use the electron source to analyze single-layer and multi-layer graphene, in order to understand what different properties emerge when it’s heated as a function of its thickness.

Filippetto said he hopes that Berkeley Lab will use HiRes in the future to dissect processes such as photosynthesis and water-oxidation and simulate reactions that accurately resemble them.

“We have to try to push towards something that mimics nature,” Filippetto said. “We want to understand nature and try to mimic the process.”

Contact Harini Shyamsundar at [email protected] and follow her on Twitter at @hshyamsundar.