Ångström
From Wikipedia, the free encyclopedia
| 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 or aangstroem (the official transliteration), or angstrom (symbol Å) is a non-SI unit of length that is internationally recognized, equal to 0.1 nm. It is sometimes used in expressing the sizes of atoms, lengths of chemical bonds and visible-light spectra. It is named after Anders Jonas Ångström.
[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 millimetre, or 1×10−10 metres. 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 metre, which was still defined based on a physical prototype. In 1960, the metre itself was redefined in spectroscopical terms, making the ångström obsolete.
[edit] Representation in computers
Unicode includes the "angstrom sign" at U+212B (Å). However, the "angstrom sign" is normalized into U+00C5 (Å), and is thereby seen as a (pre-existing) encoding mistake, and it is better to use U+00C5 (Å) directly.
When typing “ångström” or “Å”, the following key sequences create the needed characters on various English-language keyboard layouts:
- Å: ALT+0197 (Holding ALT, press and release 0, then 1, then 9, then 7, then release ALT.)
- å: ALT+0229 (Holding ALT, press and release 0, then 2, then 2, then 9, then release ALT.)
- ö: ALT+0246 (Holding ALT, press and release 0, then 2, then 4, then 6, then release ALT.)
Alternatively, you can use the "character map" on a Windows computer, found under the Start Menu, Programs, Accessories, System Tools. This program allows you to find a character in one of many different fonts and then copy and paste the character where ever you want to put it.
Apple Computer’s Mac OS (including Mac OS X)
- Å: Option-A
- å: Option-a
- ö: Option-u, then o
Or, in the Mac OS X, in the “Edit” menu, select “Special Characters…” to open a palette to find and use any character.
