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A femtosecond is the SI unit of time 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.〔(【引用サイトリンク】Merriam Webster Online Dictionary ">url = http://www.merriam-webster.com/dictionary/femtosecond )〕 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.〔Compared with overview in: Page 3〕 The word femtosecond is formed by the SI prefix ''femto'' and the SI unit ''second''. Its symbol is fs.〔(【引用サイトリンク】url = http://physics.nist.gov/cuu/Units/prefixes.html )〕 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.〔(【引用サイトリンク】LAMMPS Molecular Simulator ">url = http://lammps.sandia.gov/doc/run_style.html )〕 * The waves of visible light oscillate with a period (reciprocal frequency) of about 2 femtoseconds . 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. * * 1.3 fs – cycle time for 390 nanometer light, at the transition between violet visible light and ultraviolet〔 * * 2.57 fs – cycle time for 770 nanometer light, at the transition between red visible light and near-infrared〔 * 15 fs – the swiftest chemical reaction, such as the absorption of a light photon in the Photosynthetic antenna molecule * 200 fs – the average chemical reaction, such as the reaction of pigments in an eye to light〔 * 300 fs – the duration of a vibration of the atoms in an iodine molecule Longer Times == See also == * Femtochemistry * Femtosecond pulse shaping * Ultrafast laser spectroscopy * SI unit * Second * Microsecond * Millisecond * Nanosecond * Picosecond * Orders of magnitude (time) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「femtosecond」の詳細全文を読む スポンサード リンク
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