Blink and you’ll miss this electron: super-fast molecule snapshot

Scientists have found a new way of observing electrons – an astonishing feat given the speeds they move at.

Electrons are subatomic particles which move around the much larger atom nucleus. They travel at the speed of attoseconds – one quintillionth of a second. There are about twice as many attoseconds in a second as there have been seconds since the beginning of the universe.

The German and US team used powerful lasers to observe the electron’s behaviour when the water molecule it belongs to is hit with an X-ray.

“Until now, radiation chemists could only resolve events at the picosecond timescale, a million times slower than an attosecond,” says Linda Young, a distinguished fellow at the Argonne National Laboratory, US.

“It’s kind of like saying ‘I was born and then I died.’ You’d like to know what happens in between. That’s what we are now able to do.”

The researchers, who initially set out to study ionising radiation in nuclear waste, are hoping their achievement will help them to better understand how radiation influences molecules.

The study is published in Science.

The researchers used an X-ray free electron laser to examine electrons in a flat, thin sheet of water. Their technology, at the SLAC National Accelerator Laboratory, leans on research that won the 2023 Nobel Prize in Physics for observing things at attosecond pace.

Thin sheet of water close up
To record the movement of electrons excited by X-ray radiation, scientists create a thin, approximately 1 centimeter-wide, sheet of liquid water as a target for the X-ray beam. Credit: Emily Nienhuis | Pacific Northwest National Laboratory

“We now have a tool where, in principle, you can follow the movement of electrons and see newly ionised molecules as they’re formed in real-time,” says Young.

They were able to spot electrons absorbing X-rays and becoming more excited, before the bigger atomic nucleus sprang into action.

As well as providing proof-of-concept, the research helped to explain perplexing X-ray signals seen in previous water experiments.

“Basically, what people were seeing in previous experiments was the blur caused by moving hydrogen atoms,” says Young. “We were able to eliminate that movement by doing all of our recording before the atoms had time to move.”

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