Femtosecond – Wikipedia

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One quadrillionth of a second

A femtosecond is a unit of time in the International System of Units (SI) equal to 10-15 or 1⁄1 000 000 000 000 000 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 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.[2]

The word femtosecond is formed by the SI prefix femto and the SI unit second. Its symbol is fs.[3]

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 simulations are on the order of 1 fs.[4]
  • The periods of the waves of visible light have a duration of about 2 femtoseconds.
The colors of the visible light spectrum[6]
Color Wavelength
interval 		Cycle time
interval
Red ~ 700–635 nm ~ 2.3–2.1 fs
Orange ~ 635–590 nm ~ 2.1-2.0 fs
Yellow ~ 590–560 nm ~ 2.0-1.9 fs
Green ~ 560–520 nm ~ 1.9-1.7 fs
Cyan ~ 520–490 nm ~ 1.7-1.6 fs
Blue ~ 490–450 nm ~ 1.6-1.5 fs
Violet ~ 450–400 nm ~ 1.5-1.3 fs

Examples[edit]

  • 46 fs – the swiftest chemical reaction known (radiolysis of water leads to the formation of a H2O+ ion, which rapidly reacts to become hydronium (H3O+) and a short lived hydrogen monoxide molecule (OH))[7]
  • 200 fs – the average chemical reaction, such as the reaction of pigments in an eye to light[5]
  • 300 fs – the duration of a vibration of the atoms in an iodine molecule[8]

See also[edit]

References[edit]

  1. ^ “Femtosecond: Merriam Webster definition”. Merriam Webster Online Dictionary.
  2. ^ Compared with overview in: Fisher, Bruce; Harvey, Richard P.; Champe, Pamela C. (2007). Lippincott’s Illustrated Reviews: Microbiology (Lippincott’s Illustrated Reviews Series). Hagerstown, MD: Lippincott Williams & Wilkins. ISBN 978-0-7817-8215-9. Page 3
  3. ^ NIST. “NIST Definitions of the SI units”.
  4. ^ “Femtosecond: use in molecular dynamics simulation”. LAMMPS Molecular Simulator.
  5. ^ a b Andrew M. Weiner (2009). Ultrafast Optics. Wiley. ISBN 978-0-471-41539-8.
  6. ^ Craig F. Bohren (2006). Fundamentals of Atmospheric Radiation: An Introduction with 400 Problems. Wiley-VCH. p. 214. Bibcode:2006fari.book…..B. ISBN 978-3-527-40503-9.
  7. ^ Loh, Z.-H.; Doumy, G.; Arnold, C.; Kjellsson, L.; Southworth, S. H.; Al Haddad, A.; Kumagai, Y.; Tu, M.-F.; Ho, P. J.; March, A. M.; Schaller, R. D.; Bin Mohd Yusof, M. S.; Debnath, T.; Simon, M.; Welsch, R. (2020-01-10). “Observation of the fastest chemical processes in the radiolysis of water”. Science. 367 (6474): 179–182. doi:10.1126/science.aaz4740. ISSN 0036-8075.
  8. ^ Abbi, S. C. (2001). Nonlinear Optics and Laser Spectroscopy. United States of America: Alpha Science Int’l Ltd. p. 361. ISBN 8173193541.



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