An attosecond (symbol as) is a unit of

time Time is the continued sequence of existence and event (philosophy), events that occurs in an apparently irreversible process, irreversible succession from the past, through the present, into the future. It is a component quantity of various me ...

in the

International System of Units The International System of Units, known by the international abbreviation SI in all languages and sometimes pleonastically as the SI system, is the modern form of the metric system and the world's most widely used system of measurement. ...

(SI) equal to 1×10⁻¹⁸ of a second (one quintillionth of a second). For comparison, an attosecond is to a second what a second is to about 31.71 billion years.Electron Motion Filmed
28 February 2008 The word "attosecond" is formed by the

prefix A prefix is an affix which is placed before the stem of a word. Adding it to the beginning of one word changes it into another word. For example, when the prefix ''un-'' is added to the word ''happy'', it creates the word ''unhappy''. Particul ...

''atto'' and the unit ''second''. ''Atto-'' was derived from the Danish word for eighteen (''atten''). Its symbol is as. An attosecond is equal to 1000 zeptoseconds, or of a

femtosecond A femtosecond is a unit of time in the International System of Units (SI) equal to 10 or of a second; that is, one quadrillionth, or one millionth of one billionth, of a second. For context, a femtosecond is to a second as a second is to about 31 ...

. 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 A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless, so they alwa ...

across "the average bond length of molecular hydrogen" * 24 attoseconds: the atomic unit of time * 43 attoseconds: the shortest pulses of laser light yet created * 53 attoseconds: the second-shortest pulses of laser light created * 82 attoseconds (approximately):

half-life Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable ...

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

of a neutral pion * 100 attoseconds: fastest-ever view of molecular motion * 320 attoseconds: estimated time it takes

electron The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have n ...

s to transfer between atoms

References

{{DEFAULTSORT:1 E-18 S Orders of magnitude (time)

See also

References