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Nitrogen is a chemical element; it has symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at seventh in total abundance in the Milky Way and the Solar System.
The separation of Wolf–Rayet stars from spectral class O stars of a similar temperature depends on the existence of strong emission lines of ionised helium, nitrogen, carbon, and oxygen, but there are a number of stars with intermediate or confusing spectral features. For example, high-luminosity O stars can develop helium and nitrogen in ...
Strong spectral lines in the visible part of the electromagnetic spectrum often have a unique Fraunhofer line designation, such as K for a line at 393.366 nm emerging from singly-ionized calcium atom, Ca +, though some of the Fraunhofer "lines" are blends of multiple lines from several different species.
A wide variety of absorption band and line shapes exist, and the analysis of the band or line shape can be used to determine information about the system that causes it. In many cases it is convenient to assume that a narrow spectral line is a Lorentzian or Gaussian , depending respectively on the decay mechanism or temperature effects like ...
The spectrum of molecules has advantages over atomic spectral lines, as atomic lines are often very strong, and therefore only come from high in the atmosphere. Also the profile of the atomic spectral line can be distorted due to isotopes or overlaying of other spectral lines. [ 6 ]
O-type stars are classified by the relative strength of certain spectral lines. [1] The key lines are the prominent He + lines at 454.1 nm and 420.0 nm, which vary from very weak at O9.5 to very strong in O2–O7, and the He 0 lines at 447.1 nm and 402.6 nm, which vary from absent in O2/3 to prominent in O9.5.
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Forbidden lines of nitrogen ([N II] at 654.8 and 658.4 nm), sulfur ([S II] at 671.6 and 673.1 nm), and oxygen ([O II] at 372.7 nm, and at 495.9 and 500.7 nm) are commonly observed in astrophysical plasmas. These lines are important to the energy balance of planetary nebulae and H II regions.