Laser sources, atomic emission spectroscopy

In the application of atomic emission spectroscopy for quantitative analysis, samples must be prepared in liquid form of a suitable solvent unless it is already presented in that form. The exceptions are solids where samples can be analysed as received using rapid heating electro-thermal excitation sources, such as graphite furnace heating or laser ablation methods. Aqueous samples, e.g. domestic water, boiler water, natural spring, wines, beers and urines, can be analysed for toxic and non-toxic metals as received with... 

Because of the unique characteristics of their emitted energies, lasers have been used for sample vaporization and excitation sources in atomic emission spectroscopy. They also have been used as sources for atomic absorption and atomic fluorescence analysis. Their application in these areas will no doubt increase as lasers become cheaper and more readily available. 

Lasers (see Chapter 9) are sources of intense, monochromatic radiation which are ideal for Raman spectroscopy and have entirely replaced atomic emission sources. They are more convenient to use, have higher intensity and are more highly monochromatic for example, the line width at half-intensity of 632.8 nm (red) radiation from a helium-neon laser can be less than 0.05 cm. ... 

Since the mid-1960s, a variety of analytical chemistry techniques have been used to characterize obsidian sources and artifacts for provenance research (4, 32-36). The most common of these methods include optical emission spectroscopy (OES), atomic absorption spectroscopy (AAS), particle-induced X-ray emission spectroscopy (PIXE), inductively coupled plasma-mass spectrometry (ICP-MS), laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS), X-ray fluorescence spectroscopy (XRF), and neutron activation analysis (NAA). When selecting a method of analysis for obsidian, one must consider accuracy, precision, cost, promptness of results, existence of comparative data, and availability. Most of the above-mentioned techniques are capable of determining a number of elements, but some of the methods are more labor-intensive, more destructive, and less precise than others. The two methods with the longest and most successful histoty of success for obsidian provenance research are XRF and NAA. 

Many other types of atomization devices have been used in atomic spectroscopy. Gas discharges operated at reduced pressure have been investigated as sources of atomic emission and as ion sources for mass spectrometry. The glow discharge is generated between two planar electrodes in a cylindrical glass tube filled with gas to a pressure of a few torr. High-powered lasers have been employed to ablate samples and to cause laser-induced breakdown. In the latter technique, dielectric breakdown of a gas occurs at the laser focal point. 

This chapter deals with optical atomic, emission spectrometry (AES). Generally, the atomizers listed in Table 8-1 not only convert the component of samples to atoms or elementary ions but, in the process, excite a fraction of these species to higher electronic stales.. 4, the excited species rapidly relax back to lower states, ultraviolet and visible line spectra arise that are useful for qualitative ant quantitative elemental analysis. Plasma sources have become, the most important and most widely used sources for AES. These devices, including the popular inductively coupled plasma source, are discussedfirst in this chapter. Then, emission spectroscopy based on electric arc and electric spark atomization and excitation is described. Historically, arc and spark sources were quite important in emission spectrometry, and they still have important applications for the determination of some metallic elements. Finally several miscellaneous atomic emission source.s, including jlanies, glow discharges, and lasers are presented. 

See also Atomic Absorption Spectrometry Principles and Instrumentation Interferences and Background Correction Flame Electrothermal. Atomic Emission Spectrometry Principles and Instrumentation Flame Photometry. Elemental Speciation Practicalities and Instrumentation. Laser-Based Techniques. Optical Spectroscopy Radiation Sources Detection Devices. 

Minute amounts of sample material ablated with the focused radiation of a pulsed laser are transported into an independent excitation source, e.g., inductively coupled plasma (ICP) for further atomization, excitation, or ionization. The detection of target atoms after laser ablation (LA) is performed by hyphenated techniques using optical emission or mass spectrometry LA-ICP-OES laser ablation-lCP-optical emission spectroscopy LA-ICP-MS laser ablation-l CP-mass spectrometry... 

A very widely employed method for the measurement of spin-orbit state-specific rate constants is the time-resolved measurement of the concentrations of individual atomic levels after formation of these species from a suitable precursor, either by flash photolysis [13], or, more recently, by laser photodissociation. The concentrations of the various atomic reactant states are monitored by atomic absorption or fluorescence spectroscopy using atomic emission sources [14], or, for spin-orbit-excited states, by observation of the spontaneous infrared emission [15-18]. Recently, Leone and co-workers have utilized gain/absoiption of a colour centre and diode infrared laser to probe the relative populations of ground and spin-orbit excited halogen atoms produced in a chemical reaction [19] and also by photodissociation [20],... 

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