An attosecond is an SI unit of time equal to 10^-18 of a second. (one quintillionth of a second).^[1]

The word "attosecond" is formed by the prefix atto and the unit second. Atto- was made from the Danish word for eighteen (atten).^[2] Its symbol is as.

In ratio, one attosecond is to one second what one second is to the age of the universe.^[3][4]

An attosecond is equal to 1000 zeptoseconds, or 1/1000th 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:

• 1 attosecond – the time it takes for light to travel the length of three hydrogen atoms.^[5]
• 1 attosecond – estimated time it takes for an atomic nucleus to recoil.^[5]
• 24 attoseconds – the time taken for an electron to travel from one side of a hydrogen atom to the other.^[6]
• 80 attoseconds – the shortest pulses of laser light yet created.^[7]
• 100 attoseconds (approximately) – record for shortest time interval measured as of February 2004.^[8]
• 200 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.^[5]
• 320 attoseconds – estimated time it takes electrons to hop between atoms.^[9]

[edit] References

v • d • e Orders of magnitude (time), by powers of seconds Negative powers 10−44 s | ... | 10−24 s ... 10−19 s | 10−18 s ... 10−16 s | 10−15 s ... 10−13 s | 10−12 s ... 10−10 s | 10−9 s ... 10−7 s | 10−6 s ... 10−4 s | 10−3 s | 10−2 s | 10−1 s Positive powers 100 s | 10 s | 102 s | 103 s | 104 s | 105 s | 106 s | 107 s | 108 s | 109 s | 1010 s | 1011 s | 1012 s | 1013 s |1014 s | 1015 s | 1016 s | 1017 s | 1 E18 s and longer