Optical emission spectra

Mass spectra much simpler than optical emission spectra... 

Optical elements, liquid crystalline materials in, 15 116—117 Optical emission spectra, 14 833-837 plutonium, 19 671—673 Optical emission spectroscopy (OES), archaeological materials, 5 742 Optical fiber(s), 13 391-392 24 618 defects in, 11 145 drawing of, 11 141-145 fabrication of, 11 135-141 health care applications for, 13 397 overcladding of, 11 144 remote measurements using, 14 234 in sensors, 22 270-271 sol-gel processing of, 11 144-145 strength of, 11 141-145 vitreous silica in, 22 444 Optical fiber sensors, 12 614-616 Optical germanium, 12 556... 

Use of X-ray diffraction patterns or identification. Even when complete structure determination is not possible, however, much valuable information of a less detailed character may be obtained by X-ray methods. In the first place, the diffracted beams produced when X-rays pass through crystals may be recorded on photographic films or plates, and the patterns thus formed may be used quite empirically, without any attempt at interpretation, to identify crystalline substances, in much the same way as we use optical emission spectra to identify elements, or infra-red absorption spectra to identify molecules. Each crystalline substance gives its own characteristic pattern, which is different from the patterns of all other substances and the pattern is of such complexity (that is, it presents so many measurable quantities) that in most cases it constitutes by far the most certain physical criterion for identification. The X-ray method of identification is of greatest value in cases where microscopic methodsare inadequate for instance, when the crystals are opaque or are too small to be seen as individuals under the microscope. The X-ray diffraction patterns of different substances generally differ so much from each other that visual comparison... 

FIGURE 2 Nitrogen plasma optical emission spectra (after [6,7]). (a) ECR source, 250 W, MBE chamber pressure 2 x 10 5 mbar. (b) RF source, 200 W, MBE chamber pressure 2 x 10"6 mbar. 

In principle, the applications of ICP-MS resemble those listed for OES. This technique however is required for samples containing sub-part per billion concentrations of elements. Quantitative information of nonmetals such as P, S, I, B, Br can be obtained. Since atomic mass spectra are much simpler and easier to interpret compared to optical emission spectra, ICP-MS affords superior resolution in the determination of rare earth elements. It is widely used for the control of high-purity materials in semiconductor and electronics industries. The applications also cover the analysis of clinical samples, the use of stable isotopes for metabolic studies, and the determination of radioactive and transuranic elements. In addition to outstanding analytical features for one or a few elements, this technique provides quantitative information on more than 70 elements present from low part-per-trillion to part-per-million concentration range in a single run and within less than 3 min (after sample preparation and calibration). Comprehensive reviews on ICP-MS applications in total element determinations are available. " ... 

Figure 4.4 Optical emission spectra (OES) measured from (A) dissociation glow and (B) negative glow in DC glow discharge of trimethylsilane (TMS) flow system, 1 seem TMS, 50 mtorr, DC power 5 W.

Figure 4.11 Optical emission spectra of cascade arc plasmas, Ar, 2000 seem, CF4, 20 seem, C2F4, 20 seem, 320 W, 0.56 torr.

Figure 16.6 Typical optical emission spectra of (a) helium plasma jet and (b) argon plasma jet, the spectra was obtained at an axial position 2.7 cm from the jet inlet conditions are (a) 3000 seem helium, 1.35 kW, and 89 Pa (b) 2000 seem argon, 0.64 kW, and 75 Pa.

Figure 16.15 The optical emission spectra of argon plasma jets (a) with addition of 10 seem nitrogen and 10 seem hydrogen, (b) with addition of 60 seem nitrogen and 2.7 seem hydrogen, and (c) with pure nitrogen addition, 60 seem nitrogen. The other conditions are 2000 seem argon, 0.64 kW, and 75 Pa.

ICP-MS is well suited for multielement analysis and for determinations such as isotope ratios. The technique has a wide dynamic range, typically four orders of magnitude, and produces spectra that are, in general, simpler and easier to interpret than optical-emission spectra. ICP-MS is finding widespread use in the semiconductor and electronics industries, in geochemistry, in environmental analyses, in biological and medical research, and in many other areas. 

Figure 20 [201] shows optical emission spectra from nanoaluminum/NC samples as a function of laser fluence. The lowest fluence J = 0.4 J/cm is just enough to melt the A1 particles, and the highest fluence J = 5.2 J/cm is just enough to totally vaporize the particles. The first observable light emission is detected near the melting point. It is broad and structureless and is consistent with a blackbody t5q)e emission. At fluences where the A1 starts to vaporize, a... 

Fig. 20. left) Optical emission spectra from a suspension of A1 nanoparticles in nitrocellulose oxidizer (NC) after laser flash heating at the indicated fluences. Higher resolution spectra of the features indicated by i)-(iv) are shown in the insets. These features are attributed to AlO emission at surfaces or gas pockets. Reproduced from ref. [201]. 

Usually, atomic mass spectra are considerably simpler and easier to interpret than optical emission spectra. This property is particularly important for samples that contain rare earth elements and other heavy metals. such as iron, that yield complex emission spectra. Figure 11-15b illustrates this advantage. This spectral simplicity is further illustrated in Figure 11-16. which is the atontic mass spectrum for a mixture of fourteen rare earth elements that range in atomic mass number from 1.39 to 175. T he optical emission spectrum for such a mixture would be so complex that interpretation would be tedious, time-consuming, and perhaps impo.ssible. 

The optical emission spectra for isotopes are slightly different since electronic energy levels are depradent on the atomic masses. The light emitted when an electron falls from an outer orbit of main quantum number /t2 fo an inner orbit of quantum number /ij ( < /I2) is given by... 

The search for radio galaxies led to the unexpected discovery of what became known as quasi-stellar objects, QSO s, or quasars. The first quasars to be discovered were all strong radio sources, but the majority known today are radio silent. More characteristically, most of them are X-ray sources. However, the most characteristic property of quasars is the unusually large redshifts of their optical emission spectra. Analyses of the physical properties of quasars and speculation about their nature are tainted by the conviction that these redshifts are fully accounted for by Hubble s law. 

As discussed earlier in this text, x-ray spectra are decidedly simpler than optical emission spectra, but even so, spectral line interferences do occur. Table 8.1 lists several types of spectral line interference commonly encountered in x-ray spectrochemical analysis using wavelength dispersion. 

Figure 2. Optical emission spectra of (a) Ar and (b) OfAr plasma generated in ambient air (rf power = 200 W).(IO)...

Mahapatra S, Koppel H (1998) Quantum mechanical study of optical emission spectra rydberg-excited hj and its isotopomers. Phys Rev Lett 81 3116... 

Optical Emission Spectra Acetone Triplet in Aqueous Solution... 

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