Generation of attosecond pulses.ICFO
Electrons just got caught in the act.
For decades, scientists have known that electrons quietly dictate almost everything, including how chemical reactions unfold, how materials conduct electricity, how energy moves through biological molecules, and how quantum technologies function.
The problem has never been theory. It has been time.
Electron motion unfolds on attosecond timescales, far too fast for conventional instruments to resolve.
That barrier has now been shattered. Researchers have generated a 19.2-attosecond soft X-ray pulse, effectively building the fastest camera ever made, one capable of capturing electron dynamics in real time with unprecedented clarity.
Developed by scientists at ICFO, the pulse is the shortest and brightest soft X-ray flash ever produced.
At just 19.2 attoseconds long, it opens a direct window into processes that have never been observed before, allowing researchers to watch electrons move as reactions, phase transitions, and energy transfers actually happen.
Soft X-ray light is uniquely powerful because it can fingerprint specific atoms.
These ultrashort flashes allow scientists to track how electrons reorganize around individual atomic sites, revealing how materials change their properties or how molecules transform during reactions.
Creating an isolated pulse, this brief was far from trivial. It required major advances in high-harmonic generation, sophisticated laser engineering, and new methods of attosecond metrology.
Together, these innovations pushed pulse measurement beyond previous limits, making it possible to confirm durations that were once only inferred.
The achievement did not appear overnight. The journey began in 2015, when Prof. Jens Biegert’s team first succeeded in isolating attosecond pulses in the soft X-ray regime.
A decade-long pursuit
Those early breakthroughs already demonstrated their power, resolving how electrons interact with crystal lattices in solids and revealing how molecular rings open—an early step in processes like polymerization.
At the time, however, accurately measuring the pulse duration remained a challenge. Existing techniques lacked the precision needed to definitively pin down how short the flashes really were.
That limitation lingered for nearly a decade.
The breakthrough came with a new pulse retrieval method.
“When I came to the group and saw the streaking traces, I had to look into this with a new pulse retrieval method,” said first author Dr. Fernando Ardana-Lamas.
“Finally, we can say that, to the best of our knowledge, we have confirmed the shortest pulse of light in the world!”
The confirmation marked a new record, pushing attosecond science below what is known as the atomic unit of time, a fundamental threshold in ultrafast physics.
Watching electrons move
The implications stretch across disciplines. Being able to observe electron motion directly could transform how scientists study photovoltaics, catalysis, correlated materials, and next-generation quantum devices.
“This new capability paves the way for breakthroughs in physics, chemistry, biology, and quantum science,” said Prof. Biegert, pointing to the ability to directly observe processes that define how matter behaves at its most fundamental level.
For researchers, the pulse is not just faster, it is brighter, cleaner, and more precise, offering a tool that matches the natural timescale of electrons themselves.
With the foundations now in place, the field is poised to move from indirect inference to real-time observation.
As Prof. Biegert puts it, now that the groundwork has been laid, “the sky is the limit,”
