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Preferred term

D line  

Definition

  • One of the pair of yellow lines in emission spectra of neutral sodium (Na I). D1 has a wavelength of 5895.94 Å and D2 is 5889.97 Å. This sodium doublet is one of the strongest absorption features in the spectra of late-type stars. Labelled D in a sequence of alphabetical letters first used by Joseph von Fraunhofer to designate spectral features in the solar spectrum. (An Etymological Dictionary of Astronomy and Astrophysics, by M. Heydari-Malayeri, https://dictionary.obspm.fr/index.php?formSearchTextfield=d+line&formSubmit=Search&showAll=1)

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http://data.loterre.fr/ark:/67375/MDL-J27SRTNT-Q

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