What does attosecond mean?
An attosecond is an extraordinarily small unit of time equal to one quintillionth of a second, or 10⁻¹⁸ seconds. It belongs to the family of SI-accepted metric prefixes for time and sits three orders of magnitude below the femtosecond. To grasp its scale, there are roughly as many attoseconds in one second as there are seconds in the entire age of the universe. The word is essentially confined to scientific usage, appearing in atomic physics, ultrafast optics, and metrology. Its importance grew after the development of attosecond laser pulses in the early 2000s — a breakthrough recognised with the 2023 Nobel Prize in Physics — which allowed scientists to photograph, in effect, the motion of electrons around atoms, the fastest events directly observable by humans. Because chemical reactions and electronic processes in matter unfold on these timescales, the attosecond has become the fundamental unit for studying the most rapid dynamics in nature.
nounOne quintillionth of a second (10⁻¹⁸ s), an SI-accepted unit of time used chiefly in physics to measure ultrafast events such as electron motion within atoms.
- The unit of time equal to 10⁻¹⁸ of a second, used in ultrafast science and laser physics.
"Using attosecond laser pulses, physicists captured electrons moving in real time for the first time."
"The researchers generated an attosecond burst of X-ray light to observe electron dynamics inside a helium atom."
"Chemical bonds break on a timescale of tens of femtoseconds, but the underlying electron rearrangement unfolds within attoseconds."
Standard plural; typically used when referring to multiple pulses or measurements.
"The experiment produced pulses lasting just a few hundred attoseconds."
An attosecond is to one second what one second is to about 31.7 billion years — longer than the age of the universe.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of attosecond
The word combines 'atto-', the SI metric prefix denoting 10⁻¹⁸, adopted officially in 1964, with 'second', from Latin 'secunda', short for 'secunda minuta' (the 'second minute' following the first minute of an hour). The prefix 'atto-' derives from Danish or Norwegian 'atten', meaning 'eighteen', reflecting the convention of naming very small prefixes from Scandinavian languages (as with 'femto-' from Danish 'femten'). The compound word arose in late twentieth-century scientific literature as laser technology advanced toward ever-shorter pulses.
Related word forms
How attosecond is actually used
Attosecond is a technical, scientific term, encountered almost exclusively in physics literature, news coverage of scientific breakthroughs, and metrology contexts. It is not used colloquially.
Easily confused with attosecond
A femtosecond is one quadrillionth of a second (10⁻¹⁵ s), a thousand times longer than an attosecond.