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Fraunhofer lines

(dark lines discovered in the Sun's spectrum two centuries ago)

Fraunhofer lines are absorption lines in the Sun's optical spectrum that were found centuries ago, being the obvious ones. Some are revealed to be multiple lines at current spectral resolutions. Their original Fraunhofer line labels are mostly unused now, but occasionally seen. Each label is a letter, optionally with a subscript, with upper-case an lower-case letters indicating different lines, and upper-case letters A through K being for the prominent lines. Examples:

designationnmsource
A759.4terrestrial oxygen
B686.7terrestrial oxygen
C656.3hydrogen (H-alpha)
D1589.6neutral sodium (Na I)
D2589.0neutral sodium
E527.0neutral iron (Fe I)
F486.1hydrogen (Hβ)
H396.8ionized calcium (CA II)
K393.4ionized calcium

A term still seen occasionally is Fraunhofer's G band (or just G band) for the Fraunhofer G line, which was actually multiple lines of nearly the same wavelength in the vicinity of 429.5-431.5 nm.


(spectrography,Sun,lines)
Further reading:
http://en.wikipedia.org/wiki/Fraunhofer_lines

Referenced by pages:
G band
spectral line designation

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