Spectroscopy astrophysical

Stellar spectra normally consist of absorption lines which occur when the intense continuum radiation from the hot interior of the star is filtered on passing through the cooler outer stellar atmosphere. The strength of the absorption line is a measure of the abundance of the element. As a measure in the determination of the number of absorbing atoms the so-called equivalent width of the spectral line is used. The equivalent width is defined as the width of a square box that covers the same surface as the actual absorption profile of the line, as illustrated in Fig.6.79. An example of an experimentally recorded stellar line is included in the figure. 

The relation between equivalent width and the number of absorbing atoms is called the curve of growth. Clearly, the transition probability for 

O Lines of neutral and ionized He, and of multiply ionized light elements. 

B Lines of He and of singly ionized light elements. Hydrogen Balmer series appears. 

A Strong hydrogen Balmer series. Neutral and singly ionized metal lines. 

Lines of neutral and ionized He, and of multiply ionized light elements. Lines of He and of singly ionized light elements. Hydrogen Balrner scries appears. 

Strong hydrogen Balrner series. Neutral and singly ionized metal lines. Hydrogen Balrner series weaker. The Fraunhofer K and H lines due to Ca become very strong. 

Lines of neutral metals dominate the spectrum. Molecular bands of GN and CH appear. 

The lines of neutral metals aud the molecular bands become even stronger than in class G. Bands of TiO appear. 

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Astrophysical spectroscopy is not limited to visible frequencies but also extend to ultraviolet. X-ray, 7-ray, infrared, microwave and radio frequencies, special applications of which are to be discussed. 

After a short historical overview of the history of astrophysical spectroscopy some general properties of star forming regions will be discussed. The bipolar flow region L1228 will be shown as an example and a theoretical model for bipolar flow mechanism is proposed. 

Microwave spectroscopy is used for studyiag free radicals and ia gas analysis (30). Much laboratory work has been devoted to molecules of astrophysical iaterest (31). The technique is highly sensitive 10 mole may suffice for a spectmm. At microwave resolution, frequencies are so specific that a single line can unambiguously identify a component of a gas mixture. Tabulations of microwave transitions are available (32,33). Remote atmospheric sensing (34) is illustrated by the analysis of trace CIO, O, HO2, HCN, and N2O at the part per trillion level ia the stratosphere, usiag a ground-based millimeter-wave superheterodyne receiver at 260—280 GH2 (35). 

Abstract This tutorial shows how fundamental is the role plaid by interferences in many of the physical processes involved in astrophysical signal formating and consequently instmmentation. It is obvious in interferometry. Grating spectroscopy is explained within the same framework as Young experiment, and Fabry-Perot filters are explained as Michelson interferometers.Polarization interferences, used in Lyot filters, are discussed, emphasizing the analogy with echelle gratings. 

The data sources can be classified into tangible , for which samples can be directly handled and analyzed by chemical and other laboratory methods, and intangible requiring spectroscopy, remote sensing or considerations from theoretical astrophysics. Table 3.1 lists some typical objects and methods relating to each class. 

W.C. Martin, Sources of Atomic Spectroscopy Data for Astrophysics , in PL. Smith and W. L. Wiese (eds.), Atomic and Molecular Data for Space Astronomy Needs, Analysis and Availability, Springer, Berlin, 1992. 

The initial stages of this work were supported by the European Commission through contract no. HPRN-CT-2000-00022 Spectroscopy of Highly Excited Rovibrational States . The final stages were also supported by the European Commission (contract no. MRTN-CT-2004-512202 Quantitative Spectroscopy for Atmospheric and Astrophysical Research ). The work of PJ is supported in part by the Deutsche Forschungsgemeinschaft and the Fonds der chemischen Industrie. 

Infrared spectroscopy 100-1500 Intensity 1 of rotational lines of light molecules Boltzmann factor for rotational levels related to I Also Doppler line broadening useful, principal applications to plasmas and astrophysical observations, proper sampling, lack of equilibrium, atmospheric absorption often problems... 

Beyond the violet, France is present in all areas of astrophysics, from UV through X to gamma rays. Just mentioning the main items devoted to spectroscopy, France is involved in the satellites FUSE, XMM and INTEGRAL. 

William Frederick Meggers. Physicist at the U. S. Bureau of Standards since 1914. Chief of die spectroscopy section. Author of many papers on optics, astrophysics, photography, measurement of wave-length standards, and description and analysis of spectra. The instrument in the foreground is a concave grating spectrograph, used for photographing the emission spectrum of rhenium (41). 

We know today that hydrogen and helium are overwhelmingly the most abundant species in the atmospheres of the outer planets, but direct evidence for their presence was virtually absent prior to the work mentioned [145]. Supermolecular spectroscopy had to be discovered before such evidence could be understood and it comes as no surprise that soon after Welsh s discovery many other uses of collision-induced absorption were pointed out in various astrophysical studies. Supermolecular absorption and emission have become the spectroscopy of the neutral, dense regions, especially where non-polar gases prevail. 

Several applications of IR spectroscopy to astrophysics have been made. Small amounts of methane in the earth s atmosphere have been detected by the observation of weak IR absorption lines in solar radiation that has passed through the earth s atmosphere. Intense IR absorption bands of CH4 have been found in the spectra of the atmospheres of Jupiter, Saturn, Uranus, and Neptune. Bands of ammonia have been observed for Jupiter and Saturn bands of C02 have been observed in the Venusian spectrum and bands of H20 have been observed in the Martian spectrum. 

For many reasons atomic spectroscopy continues to be one of the most rapidly developing branches of physics. This is primarily due to the creation of very stable and monochromatic lasers, allowing one to selectively excite various atomic states, to create very highly excited (Rydberg) atoms, and due to the occurrence of new possibilities, given by non-atmospheric astrophysics, which allow one to register the electromagnetic radiation... 

In stellar astronomy, spectroscopic studies are indirectly revealing the structure deep down in stars where one could not see otherwise. An internal structure shows up in the emergent radiation spectrum both kinematically and through abundance anomalies. The solution of the solar corona line problem in 1942 may serve as a typical example of astrophysical applications of atomic spectroscopy [256]. 

The dialogue between users and providers of atomic data is a two-way conversation, with atomic physicists beginning to view astrophysical and laboratory plasmas as unique sources of new information about the structure of complex atomic species. A number of monographs on theoretical atomic spectroscopy cowritten by theoreticians and astrophysicists and dedicated to astrophysicists also contribute to better mutual understanding [18, 320]. 

A. Dalgarno and D. Leyzer (eds). Spectroscopy of Astrophysical Plasmas, Cambridge University Press, London, 1987. 

In astrophysics, there has been a requirement for much improved spectroscopy of highly charged ions. 

The monograph is dedicated to those who are interested in the theory of many-electron atoms and ions, including very highly ionized ones, in the fundamental and applied spectroscopy of both laboratory (laser produced, thermonuclear, etc.) and non-atmospheric astrophysical low-and high-temperature plasma. To some extent it may serve as a reference book and textbook for physicists and astrophysicists. 

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