Pulsed glow discharge

In conclusion, GD-OE S is a very versatile analytical technique which is still in a state of rapid technical development. In particular, the introduction of rf sources for non-conductive materials has opened up new areas of application. Further development of more advanced techniques, e. g. pulsed glow discharge operation combined with time-gated detection [4.217], is likely to improve the analytical capabilities of GD-OE S in the near future. 

Glow discharge is essentially a simple and efficient way to generate atoms. Long known for its ability to convert solid samples into gas-phase atoms, GD techniques provide ground-state atoms for atomic absorption or atomic fluorescence, excited-state atoms for atomic emission, and ionised atoms for MS [158], Commercial instrumentation has been developed for all these methods, except for GD-AFS and pulsed mode GD. 

Several recent reviews deal with GD-OES [157,162, 163] and pulsed glow discharge [164,165]. Several books on GDS have appeared [158,166,167]. 

Yet another approach is to influence the combustion process itself by ionization, pulsed electromagnetic fields, glow discharge etc. The Institute of Energy at Dnepropetrovsk State University developed a plasma-activated sparking plug, currently in preparation for a full-scale production. 

Stimulated (laser) excimer emission can be generated in pulsed high-pressure glow discharges. Dielectric barrier (silent) discharges or micro-wave discharges can be used to produce quasi-stationary or continuous incoherent excimer radiation. 

A. C. Muniz, J. Pisonero, L. Lobo, C. Gonzalez, N. Bordel, R. Pereiro, A. Tempez, P. Chapon, N. Tuccitto, A. Licciardello and A. Sanz-Medel, Pulsed radiofrequency glow discharge time of flight mass spectrometer for the direct analysis of bulk and thin coated glasses, J. Anal. At. Spectrom., 23, 2008, 1239-1246. 

Figure 5. Observed change in the elemental surface composition of hydrocarbon-covered 304 stainless steel and Inconel as a function of exposure to hydrogen discharge cleaning. The stainless steel sample was exposed to glow discharge cleaning in the PDXTokamak (Ref. 37J and the Inconel sample was exposed to pulse discharge cleaning in the TFR Tokamak. Key , C SS substrate A, O SS substrate ...

Analytical glow discharges have conventionally operated with a constant negative dc potential applied to the cathode. There is no reason, however, that they can t be operated through the application of a pulsed potential, an applied rf potential, or a positive potential applied to the cathode. Many variations have been tried alone and in combination with one another. Perhaps the most interesting among these (because of the unique capabilities that it provides) is the radio-frequency-powered discharge. The analysis of nonconductors is covered extensively in a later chapter, but a brief overview is in order here. 

Additional studies addressed the advantages of pulsed gas glow discharges coupled to the FT-ICR instrument. The FT-ICR technique requires quite low pressures in the analyzer cell to obtain the highest possible mass resolving power, since... 

Figure 19 Schematic diagram of the microsecond pulsed glow discharge time-of-flight mass spectrometry (GD-TOF-MS) system. (From Ref. 55.)...

Figure 20 Microsecond pulsed mass spectra of copper in an argon glow discharge (GD) showing spectra taken at different delay times. Operating conditions cathode-orifice distance, 5 mm argon pressure, 1.0 torr pulse width, 15 psec pulse magnitude, 3.0 kV frequency, 100 Hz. (From Ref. 56.)...

Plasma polymerization is initiated via the dissociation of molecules caused by varieties of energetic species in the luminous gas phase as described in Chapter 4. It is important to recognize that the reactive species created in the luminous gas phase are not initiators of plasma polymerization. Some species, e.g., free radicals, could be initiators of some monomers that have specific functional groups under special conditions, e.g., in the off period of pulsed glow discharge and in the nonglow zone of a reactor (remote plasma). In most cases, the reactive species created in luminous gas phase are reactive building blocks of LCVD. 

Irradiation of monomer vapor does not yield substantial polymerization that is observed in plasma polymerization. In radiation polymerization, the bombardment of electrons creates the initiator for polymerization of the monomer, whereas in plasma polymerization, the bombardment of electrons produces the polymerizable species out of a nonpolymerizable organic molecule as well as of a polymerizable monomer. The polymerizable species could act as an initiator if polymerizable monomers exist, which is not affected by the glow discharge. This situation occurs only in the pulsed discharge of a polymerizable organic molecule in short duty cycle (long resting period). 

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