High-pressure arc lamps

The experiments were perfonued in a static reaction cell in a large excess of N2 (2-200 bar). An UV laser pulse (193 mu, 20 ns) started the reaction by the photodissociation of N2O to fonu O atoms in the presence of NO. The reaction was monitored via the NO2 absorption at 405 mu using a Hg-Xe high-pressure arc lamp, together with direct time-dependent detection. With a 20-200-fold excess of NO, the fonuation of NO2 followed a pseudo-first-order rate law ... 

Carboxylic esters of a-hydroxymethylbenzoin and O-acyl 2-oximinoketones were investigated by photo-CIDNP. These two classes of polymerization initiators were found fo undergo a-cleavage through the triplet state of the carbonyl and the carbonyl-analogous functional group, respectively, as the first step. A variety of ofher radical pairs was identified in these reactions, most of which have to be ascribed to the secondary photochemistry of the products rather than to pair substitution because continuous illumination with a 1000 W high pressure arc lamp was used. 

Truly incoherent white light sources convenient for cw and transient absorption spectroscopy include cw, high pressure arc lamps ( 2 kW, spectral irradiance 3 mW/ (cm l cm2 sr)) and flashlamps ( 1 spectral irradiance of a 1 mW He-Ne laser (Av 1 MHz, dQ = 10-6sr, beam waist w 0.1 cm) is 3 x 109 W/(cm-1 cm2- sr), approximately 1012 times larger than that of the most robust incoherent cw radiation source. 

The varieties of exposure sources that have found applications in UV and visible light optical lithography can be broadly divided into two groups (i) high-pressure arc lamp or incoherent sources and (ii) laser sources or temporally coherent sources. In the laser-type sources, we include all techniques and devices for radiation generation that have their basis in stimulated emission of radiation. 

Figure 2 Typical high-pressure arc lamps. (A) 150W xenon lamp, (B) 200 W mercury lamp. Dimensions in mm. (Reproduced with permission from Knowles A and Burgess C (1984) Practical absorption spectrometry. Ultraviolet Spectrometry Group. London Chapman and Hall.)...

Mercury arcs are employed in these lamps because of the spectral distribution they emit, and because mercury vapor is relatively inert. It does not attack either the glass or the electrode materials (Kirk 1982). This contributes to the long lifetimes of mercury lamps. Low pressure mercury lamps are commonly called fluorescent lamps. High pressure mercury lamps are used in industrial environments and for street lighting and floodlighting. Other applications for mercury vapor lamps include motion-picture projection, photography, and heat therapy. 

Lanthanide bromides and iodides have found important applications in a completely different field. They are added as additives in high-pressure discharge lamps in the lighting industry to improve the arc stability and the colour quality. The latter is due to the contribution of the multiline spectrum of the doped rare earths which are added to the salt mixture. Lanthanide trihalides of dysprosium, holmium, thullium, gadolinium and lutetium are used frequently for this purpose (Hilpert and Niemann, 1997). 

Irradiation. The thick sheets were irradiated with monochromatic light according to ref. [2] using an Applied Photophysics Model 5350 photo-irradiator equipped with a 900 W short arc high pressure xenon lamp, a f/3.4 monochromator and an exit lens of quartz providing illumination over an area of 1.3 by 2.4 cm at a distance of 16 cm from the lens. The illumination was uniform over the central area (0.8 by 1.7 cm) which was analyzed. The entrance slit of die monochromator was kept at 5 nm and the exit slit at 10 nm to secure enough output energy. Irradiations were performed at ambient temperatures (ca. 23°Q in air. 

Figure 4.1 Laser flash photolysis setup with a flow system that injects either of two solutions into the sample cuvette that can be emptied after every laser flash and refilled with a fresh sample solution. PMT, photomultiplier tube. The steady-state arc lamp is usually a high-pressure xenon lamp.

Photodesulfurization. l,3-DithioIe-2-thiones (2) on irradiation (300 W high pressure mercury lamp) with an equimolar amount of (1) are converted into tetrahydrofulvalenes (3) in 50-75% yield. These products arc of current interest because they form highly conductive charge-transfer complexes with tetracyano-p-quinodimethane. ... 

W ultra high pressure Hg lamp 500 W ultra high pressure Hg lamp 500 W ultra high pressure Hg lamp Mercury arc lamp source (250 mW)... 

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