Femtosecond

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A femtosecond is the SI unit of time equal to 10−15 of a second. That is one quadrillionth, or one millionth of one billionth, of a second.[1] For context, a femtosecond is to a second what a second is to about 31.7 million years.

The word femtosecond is formed by the SI prefix femto and the SI unit second. Its symbol is fs.[2]

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.

Shorter Times

  • Typical time steps for molecular dynamics simulations are on the order of 1 fs.[3]
  • The waves of visible light oscillate with a period (reciprocal frequency) of about 2 femtoseconds {\lambda\over{c}} = {(600\times10^{-9})\over{(3\times10^8)}} = 2.0\times10^{-15}. The precise period depends on the energy of the photons, which determines their color. (See wave-particle duality) This time can be calculated by dividing the wavelength of the light by the speed of light (approximately 3 x 108 m/s) to determine the time required for light to travel that distance.[4]
    • 1.3 fs – cycle time for 390 nanometer light, at the transition between violet visible light and ultraviolet[4]
    • 2.57 fs – cycle time for 770 nanometer light, at the transition between red visible light and near-infrared[4]
  • 200 fs – the swiftest chemical reactions, such as the reaction of pigments in an eye to light[4]
  • 300 fs – the duration of a vibration of the atoms in an iodine molecule[5]

Longer Times

See also [edit]

References [edit]

  1. ^ "Femtosecond: Merriam Webster definition". 
  2. ^ NIST. "[[NIST]] Definitions of the SI units".  Wikilink embedded in URL title (help)
  3. ^ "Femtosecond: use in molecular dynamics simulation". 
  4. ^ a b c d Andrew M. Weiner (2009). Ultrafast Optics. Wiley. ISBN 978-0-471-41539-8. 
  5. ^ Abbi, S. C. (2001). Nonlinear Optics and Laser Spectroscopy. United States of America: Alpha Science Int'l Ltd. p. 361. ISBN 8173193541.