Absorption-line system

Fig. 11.7. N/O vs. O/H in extragalactic H n regions and damped Lyman-a absorption line systems shown by triangles, with schematic primary and secondary tracks. Open triangles show objects where sulphur was used as a proxy for oxygen. The Sun is shown by the large filled circle. After Pettini et al. (2002a), updated to Dec 2003. Courtesy Max Pettini.

Observations of distant objects, notably high-redshift star-forming ( Lyman-break ) galaxies and absorption line systems on the line of sight to quasars, give some information on chemical evolution at epochs not too far from when the first stars and most galaxies were presumably formed. Other information comes from two related effects ... 

Cosmic chemical evolution observations 12.4.1 High-z absorption-line systems... 

DLAs and other intervening absorption-line systems are also found projected against the visual afterglows of long-duration y-ray burst sources at high redshifts. 

Figure 18. N/O abundance ratios in spiral and irregular galaxies. Open circles Garnett 1990 open diamonds Thuan et al. 1995 filled circles Garnett et al. 1999 filled squares Garnett Kennicutt 1994, Torres-Peimbert et al. 1989 plus signs Diaz et al. 1991 stars high-redshift absorption line systems from Lu, Sargent Barlow 1998. Note the very low N/O in some high-redshift systems.

In spectroscopy it is common for transitions to be observed as absorptive lines because the Boltzmaim distribution, at equilibrium, ensures a higher population of the lower state than the upper state. Examples where emission is observed, which are by definition non-equilibrium situations, are usually cases where excess population is created in the higher level by infiising energy into the system from an external source. 

In context with methane detection during offshore oil drilling, another infrared fiber optic methane sensor was reported25. The detector comprises 3 main units a microcomputer-based signal processing and control unit, a nonconducting fiber optic gas sensor, and an optical fiber cable module. The system operates at an absorption line of methane where silica fibers have very low losses. 

A laser-based detection system for NO2 gas (which is an industrial hazard and common environmental pollutant) was developed by Koybayashi et al.4. This was achieved by splitting light, from an Ar-ion multi-line laser, into two paths, one passing through a measurement gas, and the other being transmitted directly to the measurement unit as a reference signal. The detection unit contained two filters to separate the two chosen laser lines, and these were then detected on separate optical receivers. One of these chosen laser lines coincided with a strong absorption line in the NO2... 

Taking into consideration relations (3.2.4), expressions (3.2.6) for absorption lines allowed in infrared spectra (A/ 0) are the same as those obtained formerly by an alternative method which involves no sublattice concept.81 The determination of Davydov splittings as squared frequency differences (3.2.6) results in their independence from the static frequency renormalization. For structures with [Pg.62]

For more complex spin systems, a computer program PHIP+ has been developed [13, 45] which allows the expected PHIP spectra to be calculated from the chemical shifts and coupling constants of the products. Depending upon which proton pair in the product molecule stems from p-H2, different - but characteristic - polarization patterns result [14]. The patterns also depend on the sign of the coupling constants. Simple sign rules governing the relative sequence of the emission and absorption lines in the PHIP spectra (i.e., their phase ) can be formulated in similar manner to the Kaptein Rules of chemically induced dynamic nuclear polarization (CIDNP) [15]. 

Fig. 27. Heat generation and heat absorption lines for the system shown in Fig. 26.

S. Landau and E. Stenz examined the effect of low temp, and dissociation on the fluorescence of iodine vapour at low press. Fluorescence decreases as the temp, is raised, but does not cease at 800°. Dissociation destroys both fluorescence and the resonance spectra. It is therefore inferred that the complex vibrating system is not inherent in the atom, but in the molecule that the structure of the atom is relatively simple and that, in all probability, the absorption lines which are so characteristic of diatomic iodine and so sensitive to the action of monochromatic light, do not belong to the absorption spectrum of monatomic iodine. 

Special Hamiltonians. For some ions in which the zero-field interaction is very large, it is possible to see only a few of the allowed transitions. In these cases the absorption lines have sometimes been fitted to spin Hamiltonians of somewhat different character than that of Eq. (78). For example, in the 5= 1 system it may be that only the (— l ->+ 1) transition can be observed when D is very large. In this case it will be shown in Sec. IV that this absorption can be represented fairly well by solving the spin Hamiltonian... 

M. C. Yebra-Biurrun, A. Moreno-Cid and S. Cancela-Perez, Fast on-line ultrasound-assisted extraction coupled to a flow injection-atomic absorption spectrometric system for zinc determination in meat samples, Talanta, 66(3), 2005, 691-695. 

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