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abstraction > mathematical concept > number > quantity > radiation measurement > spectral feature > spectral line > absorption line

absorption line
subject			fact

absorption line	has antonym emission line
	has definition Dark line in a spectrum, produced when light or other electromagnetic radiation coming from a distant source passes through a gas cloud or similar object closer to the observer. Like emission lines, absorption lines betray the chemical composition and velocity of the material that produces them.
	has definition Dark line superposed on a continuous spectrum, caused by the absorption of light passing through a gas of lower temperature than the continuum light source.
	is a kind of spectral line
spectral line	has transition
	has equivalent width
spectral feature	has wavelength
	has width
	occurs in
	has species
radiation measurement	has unit radiation unit
number	has value

Kinds of absorption line :

• b-lines (3 facts) - A triplet of spectral lines of Mg I.
• Fraunhofer line (12 kinds, 57 facts) - Absorption line in the spectrum of the Sun, studied by Fraunhofer in 1814. The nine most prominent he labeled with capital letters (from the red end) A. B. C. D. E. F. G. H. and K. The A band and B band are now known to be groups of telluric lines due to O₂ absorption in Earth's atmosphere, and C and F are respectively known as Hα and Hβ.
• h-line (4 facts) - Singly ionized magnesium resonance line.
• interstellar line (4 kinds, 18 facts) - Sharp, distinct absorption lines superposed on stellar spectra, produced by the interstellar gas located between the source and the observer. Strongest are the D lines, followed by the H and K lines, and the K I doublet at 7699 and 7644 Å.
• K I doublet (3 facts)
• k line (4 facts) - Singly ionized magnesium resonance line.