ICFO generates ‘record’ shortest soft X-ray pulse yet – at just 19.2 as

18 Dec 2025

Researchers have “broken barriers” in attoscience with the shortest light pulse ever created.

Researchers at ICFO, the Barcelona-based photonics institute, have set a new record by generating the shortest soft X-ray pulse to date – at just 19.2 attoseconds (as) long.

This duration is shorter than the atomic unit of time (24.2 as), which is the time it takes the electron to orbit once around the hydrogen atom – the “atomic year”.

ICFO stated that this achievement “effectively creates a camera to collect data to show how matter behaves and interacts at atomic and subatomic scales with unprecedented temporal resolution.”

Electron behavior determines how chemical reactions unfold, how materials conduct electricity, how biological molecules transfer energy, and how quantum technologies operate. But electron dynamics happen at attosecond timescales—far too fast for conventional measurement tools.

Dr. Fernando Ardana-Lamas, Dr. Seth L. Cousin, Juliette Lignieres, and ICREA Prof. Jens Biegert, at ICFO, describe the achievement of this new pulse record in a paper in Ultrafast Science.

How this was achieved

The journey towards this result began in 2015, (described at the time in a Nature paper), when Biegert’s team pioneered the generation of attosecond pulses in the soft X-ray regime by successfully isolating attosecond bursts of light.

These pulses demonstrated their breakthrough utility by resolving the interaction of electrons with the crystal lattice in a solid and by elucidating how and when a molecular ring opens as a precursor to processes such as polymerization.

But, at that time, the method for pinpointing the duration had limitations that could now be overcome, leading to the demonstration of the shortest pulse ever measured.

“When I came to the group and saw the striking traces, I had to look into this with a new pulse retrieval method,” said Ardana-Lamas , first author of the Ultrafast Science paper. “Finally, we can say that, to the best of our knowledge, we have confirmed the shortest pulse of light in the world.”

Biegert added, “This new capability paves the way for breakthroughs in physics, chemistry, biology, and quantum science, enabling direct observation of processes that drive photovoltaics, catalysis, correlated materials, and emerging quantum devices. Now that the foundations are laid, the sky is the limit.”