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There are a number of effects which control spectral line shape. A spectral line extends over a tiny spectral band with a nonzero range of frequencies, not a single frequency (i.e., a nonzero spectral width). In addition, its center may be shifted from its nominal central wavelength. There are several reasons for this broadening and shift.
There is disagreement in the literature for some line designations; for example, the Fraunhofer d line may refer to the cyan iron line at 466.814 nm, or alternatively to the yellow helium line (also labeled D 3) at 587.5618 nm. Similarly, there is ambiguity regarding the e line, since it can refer to the spectral lines of both iron (Fe) and ...
The strengths of the different spectral lines vary mainly due to the temperature of the photosphere, although in some cases there are true abundance differences. The spectral class of a star is a short code primarily summarizing the ionization state, giving an objective measure of the photosphere's temperature.
The spectral colors from red to violet are divided by the notes of the musical scale, starting at D. The circle completes a full octave, from D to D. Newton's circle places red, at one end of the spectrum, next to violet, at the other. This reflects the fact that non-spectral purple colors are observed when red and violet light are mixed.
In some cases spectral lines are well separated and distinguishable, but spectral lines can also overlap and appear to be a single transition if the density of energy states is high enough. Named series of lines include the principal , sharp , diffuse and fundamental series .
There are emission lines from hydrogen that fall outside of these series, such as the 21 cm line. These emission lines correspond to much rarer atomic events such as hyperfine transitions. [1] The fine structure also results in single spectral lines appearing as two or more closely grouped thinner lines, due to relativistic corrections. [2]
Therefore, the lines seen in the image above are the wavelengths corresponding to n = 2 on the right, to n → ∞ on the left. There are infinitely many spectral lines, but they become very dense as they approach n → ∞ (the Lyman limit), so only some of the first lines and the last one appear.
In complete band spectra, there is a number lines in a band. This spectra is produced when the emitting substance is in the molecular state. Therefore, they are also called molecular spectra. It is emitted by a molecule in vacuum tube, C-arc core with metallic salt. The band spectrum is the combination of many different spectral lines ...