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 31.71 million years; a ray of light travels approximately 0.3
μm (micrometers) in 1 femtosecond, a distance comparable to the diameter of a
virus
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea.
Since Dmitri Ivanovsk ...
.
[Compared with overview in: Page 3]
The word ''femtosecond'' is formed by the
SI prefix ''femto'' and the
SI unit
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. ...
''second''. Its symbol is fs.
A femtosecond is equal to 1000
attoseconds, or 1/1000
picosecond. Because the next higher SI unit is 1000 times larger, times of 10
−14 and 10
−13 seconds are typically expressed as tens or hundreds of femtoseconds.
* Typical time steps for
molecular dynamics
Molecular dynamics (MD) is a computer simulation method for analyzing the physical movements of atoms and molecules. The atoms and molecules are allowed to interact for a fixed period of time, giving a view of the dynamic "evolution" of t ...
simulations are on the order of 1 fs.
* The
periods of the waves of visible
light
Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 te ...
have a duration of about 2 femtoseconds.
The precise duration depends on the energy of the
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 a ...
s, which determines their color. (''See
wave–particle duality
Wave–particle duality is the concept in quantum mechanics that every particle or quantum entity may be described as either a particle or a wave. It expresses the inability of the classical concepts "particle" or "wave" to fully describe the b ...
''.) This time can be calculated by dividing the
wavelength
In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats.
It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, t ...
of the light by the
speed of light
The speed of light in vacuum, commonly denoted , is a universal physical constant that is important in many areas of physics. The speed of light is exactly equal to ). According to the special theory of relativity, is the upper limit ...
(approximately 3×10
8 m/s) to determine the time required for light to travel that distance.
Examples
* 46 fs – the swiftest
chemical reaction
A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the pos ...
(
radiolysis of water leads to the formation of a H
2O
+ ion, which rapidly reacts to become
hydronium
In chemistry, hydronium (hydroxonium in traditional British English) is the common name for the aqueous cation , the type of oxonium ion produced by protonation of water. It is often viewed as the positive ion present when an Arrhenius acid i ...
(H
3O
+) and monohydrogen monoxide (OH))
* 200 fs – the average chemical reaction, such as the reaction of
pigments
A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compoun ...
in an
eye to light
[
* 300 fs – the duration of a vibration of the atoms in an iodine molecule]
See also
* Femtochemistry
* Femtosecond pulse shaping
* Ultrafast laser spectroscopy
Ultrafast laser spectroscopy is a spectroscopic technique that uses ultrashort pulse lasers for the study of dynamics on extremely short time scales ( attoseconds to nanoseconds). Different methods are used to examine the dynamics of charge car ...
* Mode-locking
Mode locking is a technique in optics by which a laser can be made to produce pulses of light of extremely short duration, on the order of picoseconds (10−12 s) or femtoseconds (10−15 s). A laser operated in this way is sometimes r ...
* Microsecond
A microsecond is a unit of time in the International System of Units (SI) equal to one millionth (0.000001 or 10−6 or ) of a second. Its symbol is μs, sometimes simplified to us when Unicode is not available.
A microsecond is equal to 1000 ...
* Millisecond
* Nanosecond
A nanosecond (ns) is a unit of time in the International System of Units (SI) equal to one billionth of a second, that is, of a second, or 10 seconds.
The term combines the SI prefix ''nano-'' indicating a 1 billionth submultiple of an SI unit ( ...
* Orders of magnitude (time)
An order of magnitude of time is usually a decimal prefix or decimal order-of-magnitude quantity together with a base unit of time, like a microsecond or a million years. In some cases, the order of magnitude may be implied (usually 1), like a ...
* Ahmed Zewail
Ahmed Hassan Zewail ( ar, أحمد حسن زويل, ; February 26, 1946 – August 2, 2016) was an Egyptian-American chemist, known as the "father of femtochemistry". He was awarded the 1999 Nobel Prize in Chemistry for his work on femtochemistr ...
References
{{DEFAULTSORT:1 E-15 S
Orders of magnitude (time)
de:Sekunde#Abgeleitete Maßeinheiten
fr:1 E-15 s