Fraunhofer line

Room-temperature fluorescence (RTF) has been used to determine the emission characteristics of a wide variety of materials relative to the wavelengths of selected Fraunhofer lines in support of the Fraunhofer luminescence detector remote-sensing instrument. RTF techniques are now used in the compilation of excitation-emission-matrix (EEM) fluorescence "signatures" of materials. The spectral data are collected with a Perkin-Elraer MPF-44B Fluorescence Spectrometer interfaced to an Apple 11+ personal computer. EEM fluorescence data can be displayed as 3-D perspective plots, contour plots, or "color-contour" images. The integrated intensity for selected Fraunhofer lines can also be directly extracted from the EEM data rather than being collected with a separate procedure. Fluorescence, chemical, and mineralogical data will be statistically analyzed to determine the probable physical and/or chemical causes of the fluorescence. 

Where the emission wavelength(s) correspond to a Fraunhofer line, then that radiation will increase both the c and d intensities and the c/d ratio will be greater than the b/a ratio, indicating the presence of a luminescent material. Algebraically, the problem can... 

The science of spectroscopy is rooted in the work of Joseph von Fraunhofer, a German physicist. He separated sunlight into its component colors using high quality diffraction gratings and prisms. In 1814, he discovered hundreds of dark lines in the sun s spectrum, now called Fraunhofer lines. He could not, however, explain their source. Scientists know now that the lines are caused by elements near the sun s surface absorbing radiation produced in the sun s interior. 

Analysis of spectra such as Fraunhofer lines is called absorption spectroscopy because it deals with atoms capturing a photon that bumps an electron into a higher energy state. Emission spectroscopy uses an external source of energy—heat, radiation, or an... 

John Dalton s Atomic hypothesis. J. Fraunhofer locates and names Fraunhofer lines A...L in solar spectrum. About the same time, Herschel discovers infrared radiation from the Sun. 

William Prout s composite atoms hypothesis. G. Kirchhoff and R. Bunsen discover spectral analysis and significance of Fraunhofer lines Kirchhoff s law. 

D line spect The yellow line that is the first line of the major series of the sodium spectrum the doublet in the Fraunhofer lines whose almost equal components have wavelengths of 5895.93 and 5889.96 angstroms respectively. de, lTn ... 

Fraunhofer linee spect The dark lines constituting the Fraunhofer spectrum. fraun, hof-or, lTnz ... 

German physicist and physical chemist. Professor of physics at Heidelberg and Berlin. Independent discoverer of the Kirchhoff-Stewart law of radiation and absorption. He explained the Fraunhofer lines of the solar spectrum, and, with Bunsen, founded the science of spectroscopic analysis and discovered the elements cesium and rubidium. 

Spectroscopy is generally considered to have started in 1666, with Newton s discovery of the solar spectrum. Wollaston repeated Newton s experiment and in 1802 reported that the sun s spectrum was intersected by a number of dark lines. Fraunhofer investigated these lines—Fraunhofer lines—further and, in 1823, was able to determine their wavelengths. 

Early workers had noted the colours imparted to diffusion flames of alcohol by metallic salts, but detailed study of these colours awaited the development of the premixed air-coal gas flame by Bunsen. In 1859, Kirchhoff showed that these colours arose from line spectra due to elements and not compounds. He also showed that their wavelengths corresponded to those of the Fraunhofer lines. Kirchhoff and Fraunhofer had been observing atomic emission and atomic absorption, respectively. 

A very familiar example is the spectrum of sunlight, which is crossed by innumerable dark lines, the Fraunhofer lines, much has been learned about the constitution of llie sun, stars, and oilier astronomical objects from the Fraunhofer lines. 

The value of 10 is determined by molecular and particulate (cloud and aerosol) scattering, and surface reflection. A small fraction of the molecular scattering is the non-conservative Rotational Raman scattering (RRS) that partially fills the solar Fraunhofer lines in the scattered radiation, creating what is commonly known as the Ring effect [15] As a result, the ratio Iq/F, where F is the extraterrestrial solar flux, contains structure that is correlated with solar Fraunhofer lines. By separating these effects, one can write... 

After Bunsen had detected and isolated caesium, spectroscopy was taken up with great enthusiasm by William Crookes, and this led to his detection and isolation of thallium in 1861.191 Crookes letters to Charles Hanson Greville Williams, who was also working with the spectroscope, and who felt he deserved some of the credit for the discovery of thallium, have been published.192 The use of spectrochemistry in the search for hitherto unknown chemical elements in Britain over the period 1860-1869 has been described. It was perceived that, like Crookes, a scientist could make his reputation by discovering a new element. This resulted in several claims for the existence of new elements that later proved to be unfounded.193 Once Kirchhoff had established beyond doubt that the dark Fraunhofer lines were caused by the same element that caused emission lines of identical wavelengths, the way was open for the chemical analysis of the atmosphere of the sun and stars. This was a process which had been declared to be an impossibility by Auguste Comte less than 30 years previously.194... 

The sensitivity of electronic configurations to gravitational fields offers an immediate explanation of the enormously different red shifts of light emitted by a quasar and by less massive objects, physically associated with the quasar. The furore [106] over the anomalous Fraunhofer lines of common metals in a quasar corona could also be defused by the conclusion that the electron configurations of elements within the quasar, and hence their spectroscopic properties, differ from their laboratory equivalents. The observed shifts are therefore not due to a fine-structure constant changing with time, but to the response of electronic energy levels to high pressure. 

This figure shows the match between the bright lines in the spectrum of iron with some of the Fraunhofer lines, proving the presence of iron in the solar atmosphere. 

D. BREWSTER [8] in 1836 gave the true explanation of the Fraunhofer lines, the absorption of light by gases in the outer layers of the sun, superimposed on a continuous spectrum emitted by the material in inner regions. 

In 1840 the first photograph of the solar spectrum was published by HERSCHEL [9] - and in 1842 E. BECQUEREL [10] published also a Daguerreplate of the solar spectrum showing beautifully the Fraunhofer lines, but it was the eighteen seventies before the gelatin-silver bromide dry plates became available. 

Again, in this period, it was controversial whether the Fraunhofer lines were a property of solar light or whether they were produced by the apparatus and further, if not by the apparatus, then by absorption in the sun or in the earth s atmosphere Indeed, some of the lines are so produced, and were identified as such. 

ANGSTROM finally drives home the nail in 1862 [15]. He recapitulates the results of his earlier works, in particular, that they had demonstrated that the spectra of mixtures or compounds presented the same lines as the constituent substances. He then makes a correspondence between lines in the emission spectra of a number of elements taken one at a time with particular groups of Fraunhofer lines identified by their distinguishing letters, remarking that the Fraunhofer lines are the inversion of the bright lines seen in electrical spectra, and eventually he turns to hydrogen ... 

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