Spectral line

GHz spectral line surveys of tliree regions of the W3 giant molecular cloud complex [21]. From such studies, which reveal dramatic differences in the THz spectmm of various objects, molecular astrophysicists hope to classify the evolutionary state of the cloud, just as optical spectra are used to classify stars. 

Dugan M A and Albrecht A C 1991 Radiation-matter oscillations and spectral line narrowing in field-correlated four-wave mixing I theory Rhys. Rev. A 43 3877-921 

The most ftmdamental limitation on sharpness of spectral lines is the so-called natural linewidth. Because an 

Gr. thallos, a green shoot or twig) Thallium was discovered spectroscopically in 1861 by Crookes. The element was named after the beautiful green spectral line, which identified the element. The metal was isolated both by Crookes and Lamy in 1862 about the same time. 

Sack R A 1958 A contribution to the theory of the exchange narrowing of spectral lines Mol. Phys. 1 163-7 

It is one of the "noble" gases. It is characterized by its brilliant green and orange spectral lines. 

Europe) In 1890 Boisbaudran obtained basic fractions from samarium-gadolinium concentrates which had spark spectral lines not accounted for by samarium or gadolinium. These lines subsequently have been shown to belong to europium. The discovery of europium is generally credited to Demarcay, who separated the rare earth in reasonably pure form in 1901. The pure metal was not isolated until recent years. 

As discussed above, the spectrum must be assigned, i.e. the quantum numbers of the upper and lower levels of the spectral lines must be available. In addition to the line positions, intensity infomiation is also required. 

NMR studies carried out on nuclei such as FI, and Si this does not really impose any limitation on their observation. Broader spectral lines can be reproduced by pulse teclmiques, provided that corrections are made for the RF-irradiation and probe responses but this requires carefiil calibration. Such corrections have been most extensively used for examining satellite transition spectra from quadnipolar nuclei [11]. 

Miscellaneous. NIST has a reference database of criticaUy evaluated x-ray photoelectron and Auger spectral data, which is designed to mn on PCs. It is searchable by spectral lines as weU as by element, line energy, and chemical data (82). The Nuclear Quadrapole Resonance Spectra Database at Osaka University of over 10,000 records is avaUable in an MS-DOS version (83). The NCLl system, SDBS, has esr and Raman spectra, along with nmr, ir, and ms data, as described. 

Velocity recoils are measured at short times after tire initial ultraviolet excitation pulse by probing tire nascent Doppler profiles for tire different spectral lines probed in tliese last steps. 

High-resolution spectroscopy used to observe hyperfme structure in the spectra of atoms or rotational stnicture in electronic spectra of gaseous molecules connnonly must contend with the widths of the spectral lines and how that compares with the separations between lines. Tln-ee contributions to the linewidth will be mentioned here tlie natural line width due to tlie finite lifetime of the excited state, collisional broadening of lines, and the Doppler effect. 

The next two temis (Lorentzians) arise from the mechanical part of the density fluctuations, the pressure fluctuations at constant entropy. These are the adiabatic sound modes (l/y)exp[-FA t ]cos[co(A) t ] with (D(k) = ck, and lead to the two spectral lines (Lorentzians) which are shifted in frequency by -ck (Stokes line) and +ck (anti-Stokes line). These are known as the Brillouin-Mandehtarn, doublet. The half-width at 

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). 

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