Spectral Line

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spectral line

[′spek·trəl ‚līn]
(spectroscopy)
A discrete value of a quantity, such as frequency, wavelength, energy, or mass, whose spectrum is being investigated; one may observe a finite spread of values resulting from such factors as level width, Doppler broadening, and instrument imperfections. Also known as spectrum line.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Spectral Line

 

a thin line in an optical spectrum. Each such line can be characterized by a certain wavelength λ or frequency v = c/λ, where c is the speed of light. Spectral lines are observed in emission spectra as bright (colored) lines on a dark background and in absorption spectra as dark lines on a bright background. Each spectral line corresponds to a definite quantum transition in an atom, molecule, or crystal. Spectral lines are not strictly monochromatic: each one has a certain width Δλ.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
The goal is to click on a dip caused by a known absorption line. That's why it's important to use a prominent A-type star for calibration.
Another feature is a strong absorption line of Mg II at 4482 [Angstrom] (Figure 3).
It will be capable of detecting and measuring the mass of the WHIM by observing oxygen and other elemental absorption lines by foreground clouds in the spectra of quasars with orders of magnitude more sensitivity and better resolution than Chandra and XMM-Newton.
where the quantity A([bar.v] = ln([PHI]([bar.v])/[[PHI].sub.0]([bar.v])) is the spectral absorbance (Naperian), in certain cases (see, e.g., http://goldbook.iupac.org/A00028.html) also called extinction, and [A.sub.line] is the spectrally integrated area of the absorption line. Using (2) the species amount fraction can be derived from spectroscopic measurements as pointed out in previous publications [12].
FTIR (450-4000 [cm.sup.-1]) and Raman (95-3000 [cm.sup.-1]) spectra have been presented with different absorption lines and their association with corresponding vibrational modes on the basis of DFT calculations.
For the integrated line spectroscopy the magnitude to be measured is the area under a few absorption lines.
Since the late 1960s, observers have been checking to see whether the spacings between the absorption lines in quasar spectra differ slightly from those observed in laboratory experiments.
Note that there are absorption lines from various atmospheric gasses, but there are major transmission widows in the near-, mid-, and far-IR ranges.
Furthermore, infrared DIAL systems are preferred because they are highly sensitive to the laser energy, are relatively eye safe, and more importantly, are in the spectral range where most molecular-specific absorption lines occur.|3~ Of the available infrared lasers, C|O.sub.2~ lasers are the best suited for long path atmospheric monitoring because they have the highest efficiencies and powers, are easily tuned, and cover the 9.2 to 10.9 ||micro~meter~ range, which is rich in molecular-specific spectra.
Light from a star surrounded by a cloud of gas often shows absorption lines produced when starlight of a specific energy is absorbed by atoms in the gas cloud.
There were some hints that this couldn't be the case - for example, early spectrometry (looking at the wavelengths of light visible in the sun) showed that we could identify the elements in the sun, by looking at the absorption lines: