Attosecond

An attosecond (symbol as) is a unit of time in the International System of Units (SI) equal to 1×10⁻¹⁸ of a second (one quintillionth of a second).[1] For comparison, an attosecond is to a second what a second is to about 31.71 billion years.[2][3]

The word "attosecond" is formed by the prefix atto and the unit second. Atto- was derived from the Danish word for eighteen (atten).[4] Its symbol is as.

An attosecond is equal to 1000 zeptoseconds, or 1⁄1000 of a femtosecond. Because the next higher SI unit for time is the femtosecond (10⁻¹⁵ seconds), durations of 10⁻¹⁷ s and 10⁻¹⁶ s will typically be expressed as tens or hundreds of attoseconds:

Times which can be expressed in attoseconds:

• 0.247 attoseconds: travel time of a photon across "the average bond length of molecular hydrogen"[5]
• 24 attoseconds: the atomic unit of time[6]
• 43 attoseconds: the shortest pulses of laser light yet created[7]
• 53 attoseconds: the second-shortest pulses of laser light created[8][9]
• 82 attoseconds (approximately): half-life of beryllium-8, maximum time available for the triple-alpha process for the synthesis of carbon and heavier elements in stars
• 84 attoseconds: the approximate half-life of a neutral pion[10]
• 100 attoseconds: fastest-ever view of molecular motion[11][12]
• 320 attoseconds: estimated time it takes electrons to transfer between atoms[13][14]

In 2023, physicists Anne L'Huillier, Pierre Agostini and Ferenc Krausz won the Nobel Prize in Physics for creating the attosecond pulses of light - useful for study of electron dynamics in matter.[15] Their contributions have opened the field of attosecond physics.[15]