Chromospheres

In 1868, within a decade of the development of the spectroscope, an orange-yeUow line was observed in the sun s chromosphere that did not exactiy coincide with the D-lines of sodium. This line was attributed to a new element which was named helium, from the Greek hellos, the sun. In 1891 an inert gas isolated from the mineral uranite showed unusual spectral lines. In 1895 a similar gas was found in cleveite, another uranium mineral. This prominent yellow spectral line was then identified as that of helium, which to that time had been thought to exist only on the sun. In 1905 it was found that natural gas from a well near Dexter, Kansas, contained nearly 2% helium (see Gas, natural). 

LTE Abundance Analyses in Cool, Chromospherically Active Stars... 

Atoms, ions and molecules present in the stars provide additional opacity at wavelengths corresponding to specific atomic transitions these give rise to comparatively narrow absorption lines (see Fig. 3.2) with intensities related to the abundances of the relevant elements (and much else). Despite the name, processes other than pure absorption (e.g. scattering and fluorescence) are involved in the production of these lines and, while they are often treated in LTE, this is now only a simplifying approximation which often works fairly well, but needs to be checked by more detailed calculations for each particular case. (In some cases, there are even emission lines or emission components, e.g. the solar Ca+ H and K lines in the near UV, which are so strong that the chromosphere affects their central parts.)... 

Helium is the second most abundant element in the visible Universe and accordingly there is a mass of data from optical and radio emission lines in nebulae, optical emission lines from the solar chromosphere and prominences and absorption lines in spectra of hot stars. Further estimates are derived more indirectly by applying theories of stellar structure, evolution and pulsation. However, because of the relative insensitivity of Tp to cosmological parameters, combined with the need to allow for additional helium from stellar nucleosynthesis in most objects, the requirements for accuracy are very severe better than 5 per cent to place cosmological limits on Nv and better still to place interesting constraints on t] or One can, however, assert with confidence that there is a universal floor to the helium abundance in observed objects corresponding to 0.23 < Fp < 0.25. 

Helium - the atomic number is 2 and the chemical symbol is He. The name derives from the Greek helios for sun . The element was discovered by spectroscopy during a solar eclipse in the sun s chromosphere by the French astronomer Pierre-Jules-Cesar Janssen in 1868. It was independently discovered and named helium by the English astronomer Joseph Norman Lockyer. It was thought to be only a solar constituent until it was later found to be identical to the helium in the uranium ore cleveite by the Scottish chemist William Ramsay in 1895. Ramsay originally called his gas krypton, until it was identified as helium. The Swedish chemists Per Theodore Cleve and Nils Abraham Langet independently found helium in cleveite at about the same time. 

Pierre-Jules-Cesar Janssen,0 1824-1907. French astronomer who directed many astronomical expeditions. Member of the French Institute and of the Bureau of Longitude. In 1868 he observed in the sun s chromosphere a yellow line, Da, which is now known to belong to the element helium. He was the director of the astrophysical observatory at Meudon. 

Birth of Marie Sklodowska (Mme. Curie) at Warsaw, Poland. Janssen and Lockyer independently observe the D line of helium in the sun s chromosphere. 

Frankland, Sir Edward (1825—1899). A British chemist noted for research on organic-metallic compds, valency, water supply and the theory of flames. Discovered, in collaboration with Brit astronomer Sir Joseph Lockyear (1836— 1920), helium in the sun s chromosphere Ref Hackh s Diet (1944), 355-L St 498-L... 

N. Filipescu, Intramolecular energy transfer between non-conjugated chromospheres , Reference Q, p. 697. 

In 1907 Lunt [18] noted the presence of europium in the chromosphere. The extensive work of Morgan [10] on the europium type stars... 

J.D. Berset and R. Holzer, Determination of coplanar and ortho substituted PCBs in some sewage sludges of Switzerland using HRGC/ECD and HRCG/MSD, Chromosphere, 32 (1996) 2317-2333. 

Gas chromatography of phenyl urea herbicides is difficult because of their ease of decomposition. Procedures have been reported in which careful control of conditions allows these compounds to be chromatographed intact [339, 340,344,345]. Alternatively, the urns can be hydrolyzed to the corresponding substituted anilines these compounds are then determined by either gas chromatography directly [341] or as derivatives [342], or colorimetrically [343] after coupling with suitable chromospheres. Methods based on hydrolysis lack... 

By Eq. (16.22), one can observe that the intensity of fluorescence for transparent samples is directly proportional to the intensity of incident light in the sample, depending on the absorptivity of the sample in the wavelength of excitation and concentration of chromospheres. Figure 16.34a shows a typical curve for the fluorescence intensity as a function of fluorophore concentration. 

In Figure 16.34b there is a typical curve that describes Eq. (16.24). At high concentrations, even a complete extinction of the fluorescence sign can be observed. A similar behavior can occur when the sample contains chromospheres that compete for the absorption of light excitation. 

M. Saha, Ionization in the solar chromosphere, Philosophical Magazine 40 (1920) 472-488, on 476. Reprinted in Lang and Gingerich, A Source Book in Astronomy and Astrophysics 1900-1975, 236-242. 

Bob reaches into his pocket and tosses an orange to Mr. Plex. I want to talk about the Sun s structure. The Sun has an atmosphere consisting of three layers the photosphere, chromosphere, and corona. The photosphere is the visible surface of the Sun. It s about 400 kilometers (250 miles) thick. That s a bit more than the distance from New York City to Washington D.C. ... 

---