Mercury arc

Medium-pressure arc mercury lamps consist of a sealed cylindrical quartz tube with tungsten electrodes on each end. The tube contains a small amount of mercury metal and vapor and starter gas (usually argon). An example of such a lamp is shown in Figure 3.1.4... 

Figure 16. Ultraviolet spectral distribution of carbon arc, mercury arc, and fluorescent black lamp...

The matrices were photolyzed subsequent to trapping with a 100-watt short-arc mercury lamp focused down to a 1-inch diameter spot. Photolysis times and filters utilized in wavelength selective studies will be reported for each experiment in the next section. 

WATT PRESSURIZED SHORT ARC MERCURY/XENON LAMP... 

These lamps are short-arc mercury lamps containing a metal halide surrounded by a glass envelope. The metal used is generally one with a very rich line spectrum, low ionization potential, and low corrosivity. They are available as both air- and water-cooled varieties. 

High-pressure mercury arc Mercury Far-IR Best for range between 200 and 10cm ... 

The yellowish glow of some highway lamps is due to a sodium arc. Mercury lamps give a bluish glow. 

The principal sources of ultraviolet radiation are carbon arcs, xenon arcs, mercury arcs and derived fluorescent lamps. Comparison of the emission spectra of these light sources with sunlight is shown in Fig. 10 [15]. Energy characteristics of various light sources and their relation to the weatherability of plastics have been discussed by Hirt and Searle [16]. 

Primary explosives have a high degree of sensitivity to initiation through shock, friction, electric spark or high temperatures and explode whether they are confined or unconfined. Typical primary explosives which are widely used are lead azide, lead styphnale (trinilroresorci-nate), lead mononitroresorcinate (l-MNR), potassium dinitrobenzo-furozan (KDNBF), barium slyphnatcand potassium perchlorate. Other primary explosive materials which are not frequently used today arc mercury azide, potassium chlorate atid mercury fulminate. 

Among other electrophilic substitution reactions undergone by azulenes arc mercuriation [106,132] and aminomethylation [133,134]. 

FIG. 7. Spectral distribution of radiation sources in relative units deuterium ( - -). xenon arc (-mercury discharge lamps ( ) ... 

Light sources can either be broadband, such as a Globar, a Nemst glower, an incandescent wire or mercury arc lamp or they can be tunable, such as a laser or optical parametric oscillator (OPO). In the fomier case, a monocln-omator is needed to achieve spectral resolution. In the case of a tunable light source, the spectral resolution is detemiined by the linewidth of the source itself In either case, the spectral coverage of the light source imposes limits on the vibrational frequencies that can be measured. Of course, limitations on the dispersing element and detector also affect the overall spectral response of the spectrometer. 

Far-infrared Mercury arc Polymer Grating interferometer Golay cell thermocouple bolometer pyroelectric... 

The use of vibrational Raman spectroscopy in qualitative analysis has increased greatly since the introduction of lasers, which have replaced mercury arcs as monochromatic sources. Although a laser Raman spectrometer is more expensive than a typical infrared spectrometer used for qualitative analysis, it does have the advantage that low- and high-wavenumber vibrations can be observed with equal ease whereas in the infrared a different, far-infrared, spectrometer may be required for observations below about 400 cm. ... 

Laser radiation is very much more intense, and the line width much smaller, than that from, for example, a mercury arc, which was commonly used as a Raman source before 1960. As a result, weaker Raman scattering can now be observed and higher resolution is obtainable. 

Ultraviolet light sources are based on the mercury vapor arc. The mercury is enclosed ia a quart2 tube and a potential is appHed to electrodes at either end of the tube. The electrodes can be of iron, tungsten, or other metals and the pressure ia a mercury vapor lamp may range from less than 0.1 to >1 MPa (<1 to >10 atm). As the mercury pressure and lamp operating temperatures are iacreased, the radiation becomes more iatense and the width of the emission lines iacreases (17). 

Lighting. An important appHcation of clear fused quartz is as envelop material for mercury vapor lamps (228). In addition to resistance to deformation at operating temperatures and pressures, fused quartz offers ultraviolet transmission to permit color correction. Color is corrected by coating the iaside of the outer envelope of the mercury vapor lamp with phosphor (see Luminescent materials). Ultraviolet light from the arc passes through the fused quartz envelope and excites the phosphor, produciag a color nearer the red end of the spectmm (229). A more recent improvement is the iacorporation of metal haHdes ia the lamp (230,231). 

Chlorine free radicals used for the substitutioa reactioa are obtaiaed by either thermal, photochemical, or chemical means. The thermal method requites temperatures of at least 250°C to iaitiate decomposition of the diatomic chlorine molecules iato chlorine radicals. The large reaction exotherm demands close temperature control by cooling or dilution, although adiabatic reactors with an appropriate diluent are commonly used ia iadustrial processes. Thermal chlorination is iaexpeasive and less sensitive to inhibition than the photochemical process. Mercury arc lamps are the usual source of ultraviolet light for photochemical processes furnishing wavelengths from 300—500 nm. 

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