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A spectral line may be observed either as an emission line or an absorption line. Which type of line is observed depends on the type of material and its temperature relative to another emission source. An absorption line is produced when photons from a hot, broad spectrum source pass through a cooler material.
Spectral line shape or spectral line profile describes the form of an electromagnetic spectrum in the vicinity of a spectral line – a region of stronger or weaker intensity in the spectrum. Ideal line shapes include Lorentzian , Gaussian and Voigt functions, whose parameters are the line position, maximum height and half-width. [ 1 ]
In spectroscopy, the Autler–Townes effect (also known as AC Stark effect), is a dynamical Stark effect corresponding to the case when an oscillating electric field (e.g., that of a laser) is tuned in resonance (or close) to the transition frequency of a given spectral line, and resulting in a change of the shape of the absorption/emission spectra of that spectral line.
Defined in technical language, spectral music is an acoustic musical practice where compositional decisions are often informed by sonographic representations and mathematical analysis of sound spectra, or by mathematically generated spectra. The spectral approach focuses on manipulating the spectral features, interconnecting them, and ...
Line spectral pairs have several interesting and useful properties. When the roots of P(z) and Q(z) are interleaved, stability of the filter is ensured if and only if the roots are monotonically increasing. Moreover, the closer two roots are, the more resonant the filter is at the corresponding frequency.
Solar spectrum with Fraunhofer lines as it appears visually. In 1802, English chemist William Hyde Wollaston [2] was the first person to note the appearance of a number of dark features in the solar spectrum. [3] In 1814, Joseph von Fraunhofer independently rediscovered the lines and began to systematically study and measure their wavelengths ...
The Lyman-alpha forest was first discovered in 1970 by astronomer Roger Lynds in an observation of the quasar 4C 05.34. [1] Quasar 4C 05.34 was the farthest object observed to that date, and Lynds noted an unusually large number of absorption lines in its spectrum and suggested that most of the absorption lines were all due to the same Lyman-alpha transition. [2]
K line spectrum of KW 326, a dwarf star in the Praesepe open cluster. The line is very wide and very deep, and it originates in the photosphere, just like any other absorption line. Several other lines are superimposed on it. In the center, the emission due to the K line itself, which takes place in the chromosphere. Zoom on the emission core.