Ångström
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| International units | |
|---|---|
| 100×10−12 m | 100×10−15 km |
| 100×10−9 mm | 1 Å |
| 668.459×10−24 AU | 0 LY |
| US customary / Imperial units | |
| 3.937×10−9 in | 328.084×10−12 ft |
| 109.361×10−12 yd | 62.137×10−15 mi |
An ångström (symbol Å) is a non-SI unit of length that is internationally recognized. It is sometimes used expressing the size of atoms, and lengths of chemical bonds and visible-light spectra.
Contents |
[edit] Definition
For an example of lengths in this unit, the average diameter of an atom, calculated from its empirical radius, ranges from approximately 0.5 Å for hydrogen (the smallest element) to 3.8 Å for uranium (the largest naturally occurring element on earth).
[edit] History
The ångström is named after the Swedish physicist Anders Jonas Ångström (1814–1874), one of the founders of spectroscopy. Besides astrophysics, Ångström was also a student of heat transfer, terrestrial magnetism, and the aurora borealis, which was so prominent for him in his northern skies. He created a spectrum chart of solar radiation that expresses the length of electromagnetic radiation in the electromagnetic spectrum on the order of multiples of one ten-millionth of a millimeter, or 1×10-10 meters. This unit of length became known as the ångström, Å.
From 1927 to 1960, the ångström was a secondary unit of length for use in spectroscopy, defined separately from the meter, which was still defined based on a physical prototype. In 1960, the meter itself was redefined in spectroscopic terms, making the ångström obsolete.
[edit] Representation in computers
Unicode includes the "ångström sign" at U+212B (Å). However, the "ångström sign" is canonically decomposed into U+00C5 (Å), thereby seen as a (pre-existing) encoding mistake, and it is better to use U+00C5 (Å) directly.
When typing the ångström sign into Excel or other processing programs, it is important to type in [A]~0(2) + Ctrl-W in order for it to be formatted correctly. Word processors do not have this symbol directly included and so it must be input as mentioned.
On a Macintosh, the keyboard shortcut for Å is [Option-Shift-A].
[edit] See also
bs:Ångstrom br:Angström bg:Ангстрьом ca:Àngstrom da:Ångstrøm de:Ångström (Einheit) et:Ongström es:Angstrom eo:Angstromo (unuo) eu:Angstrom fa:آنگستروم fr:Angström gl:Angstrom ko:옹스트롬 hr:Ångstrom id:Angstrom it:Angstrom he:אנגסטרם nl:Ångström ja:オングストローム no:Ångstrøm nn:Ångström pl:Angstrem pt:Ångström ru:Ангстрем sk:Angström sl:Ångström sr:Ангстрем (јединица) fi:Ångström sv:Ångström th:อังสตรอม vi:Ångström tr:Angström uk:Ангстрем zh:埃格斯特朗 (单位)
