Mercury lamp radiation

For comparison the output power of a high-pressure mercury lamp (Osram HBO 200) also is listed. The reader has to consider, however, that the mercury lamp radiates this power into the unit solid angle (= 60°) distributed over the spectral range from 2000 to 6000.A, whereas the laser intensity is concentrated at a single wavelength and collimated in a beam with a very small divergence between 10 and 10" sterad. 

Figure 10.52. Cl index of neat and plasticized PVC with diisodeoyl phthalate vs. exposure time to filtered mercury lamp radiation above 290 nm. [Data from Balabanovioh A I Denizligil S Schnabel W, J. Vinyl Additive Technol, 3, No.l, March 1997, p.42-52.]...

Attempts to conduct the photochemical conversion of methane in water vapour at temperatures below 100 °C and atmospheric pressure were made in [203]. Since the first absorption band of paraffinic hydrocarbons is located in the Schumann ultraviolet region, starting from 144 nm for methane, it was assumed that the conversion of methane is initiated by hydroxyl radicals formed by water vapour photolysis. The main products were methanol (with a selectivity of 70% at 90 °C), formic add (11%), ethanol (5%), formaldehyde (5%), acetone (4%), and acetic add (3%). The photolysis was carried out with a 20-W low-pressure mercury lamp. Given that the absorption of UV radiation by water vapour starts at 185 nm, which is the lower boimdary of mercury lamp radiation transmitted by a quartz bulb, the photochemical conversion of methane in these conditions is unlikely to be sufficiently efficient. 

The first investigators to study the photodecomposition of 4-heptanone were Bamford and Norrish (1935, 1938) who had available only relatively primitive equipment and analytical techniques by today s standards. However, they managed to establish the occurrence of both radical generation in processes (I) and (II) and the Norrish type-II rearrangement in process (HI). Using filtered mercury lamp radiation (largely 248-277 nm) and a calibrated thermopile system to determine quantum yields of products of 4-heptanone photodecomposition, Bamford and Norrish (1938) reported 4>co 0.26 (15°C) 0.36 (74°C) and 0.37 (100 C) and 4>c2H4 0.45 (15 0 0.30 (74 C) and 0.29... 

In practice, o2one concentrations obtained by commercial uv devices ate low. This is because the low intensity, low pressure mercury lamps employed produce not only the 185-nm radiation responsible for o2one formation, but also the 254-nm radiation that destroys o2one, resulting in a quantum yield of - 0.5 compared to the theoretical yield of 2.0. Furthermore, the low efficiency (- 1%) of these lamps results in a low o2one production rate of 2 g/kWh (100). 

Fig. 4.18. Kinetics of variation of electric conductivity of the ZnO sensor on Si02 plate activated with Pd after leaking-in hydrogen 1 - without illuminating the plate 2 - during illumination with light at 313 nm from a mercury lamp with an additional water filter absorbing IR radiation. Stars show the beginning of sharp rise of electric conductivity.

Since chlorinated PVC is totally transparent in the near-UV and visible range, it will not absorb at 488 nm, the emission line of the argon ion laser that we intended to use to perform the carbonization. Therefore C-PVC films were first exposed to the UV radiation of a medium pressure mercury lamp in order to produce the strongly absorbing polyenes. This irradiation was carried out at room temperature in the absence of oxygen, thus preventing the formation of undesirable oxidation products. 

Since our main objective was to remove all the chlorine and hydrogen atoms from the polymer chain, C-PVC films were further exposed to the UV radiation of the medium pressure mercury-lamp. This led to a dark brown material w.hich was found to be unable to carry an electrical current, even after extended irradiation time. Therefore we turned to a powerful laser source, a 15 W argon ion laser tuned to its continuous emission at 488.1 nm. At that wavelength, the degraded polymer film absorbs about 30 % of the incident laser photons. The sample was placed on a X-Y stage and exposed to the laser beam at scanning rates in the range of 1 to 50 cm s, in the presence of air. 

When this resin was exposed as a thin film to the UV radiation of a medium pressure mercury lamp (80 W aiH), the crosslinking polymerization was found to develop extensively within a fraction of a second (18). The kinetics of this ultra-fast reaction can be followed quantitatively by monitoring the decrease of the IR absorption at 810 an-1 of the acrylic double bond (CHCH twisting). Figure 8 shows a typical kinetic curve obtained for a 20 pm thick film coated onto a NaCl disk and exposed in the presence of air to the UV radiation at a fluence rate of 1.5 x 10 6 einstein s-1 cm 2. 

Chemat and his coworkers [92] have proposed an innovative MW-UV combined reactor (Fig. 14.7) based on the construction of a commercially available MW reactor, the Synthewave 402 (Prolabo) [9[. It is a monomode microwave oven cavity operating at 2.45 GHz designed for both solvent and dry media reactions. A sample in the quartz reaction vessel could be magnetically stirred and its temperature was monitored by means of an IR pyrometer. The reaction systems were irradiated from an external source of UV radiation (a 240-W medium-pressure mercury lamp). Similar photochemical applications in a Synthewave reactor using either an external or internal UV source have been reported by Louerat and Loupy [93],... 

UVC radiation can not only be used to sterilize tap water, but also for the treatment of air and sewage. Radiation between 250 nm and 265 nm is passes through water and is strongly absorbed by nucleic acids, i.e. any living creature present. This kind of radiation therefore efficiently kills all microorganisms in the water. It is a lucky coincidence that at 254 nm, the main emission line of mercury lamps lies within the range of effective UV sterilization. 

We give two examples. The Tb3+ ion in YAI3B4O12 caimot be excited by 254 nm radiation (from a low-pressure mercury lamp), because Tb3+ in this lattice does not absorb this radiation. Ce3+ in YAI3B4O12, however, does absorb this radiation. Energy transfer from Ce3+ to Tb3+ occurs so that excitation into the Ce3+ ion is followed by Tb3+ emission 85). 

Irradiation of Sg, dissolved in CS, with the UV radiation of a mercury lamp in a quartz apparatus results in the formation of Sg, S7 and Sjj together with traces of Sg, Sjo and some polymeric insoluble material. After 10 hours the concentrations of Sg and S7 become approximately constant at levels much higher than in liquid sulfur at 160 °C see Fig. Irradiation of either one of Sg, S7 or S g in CS solution also results in mixtures of Sg, Sj and Sg... 

Light source. The most suitable light system examined was a Chromato-Vue Model C-3 from Ultra Violet Products, Inc., San Gabriel, CA. The light source was a GE G15T8, 15-W, Germicidal, 2537 bulb. The mercury lamp emitted radiation maxima at 254, 265, 280, 302, 313, 365, 405, and 436 nm. Radiation from this source passed... 

Elements such as As, Se and Te can be determined by AFS with hydride sample introduction into a flame or heated cell followed by atomization of the hydride. Mercury has been determined by cold-vapour AFS. A non-dispersive system for the determination of Hg in liquid and gas samples using AFS has been developed commercially (Fig. 6.4). Mercury ions in an aqueous solution are reduced to mercury using tin(II) chloride solution. The mercury vapour is continuously swept out of the solution by a carrier gas and fed to the fluorescence detector, where the fluorescence radiation is measured at 253.7 nm after excitation of the mercury vapour with a high-intensity mercury lamp (detection limit 0.9 ng I l). Gaseous mercury in gas samples (e.g. air) can be measured directly or after preconcentration on an absorber consisting of, for example, gold-coated sand. By heating the absorber, mercury is desorbed and transferred to the fluorescence detector. 

In the laboratory, the source of radiation may be a high-intensity mercury lamp. However, for simple test purposes, sunlight is quite suitable. Even a lightly overcast sky furnishes sufficient UV radiation for photo-induced polymerizations. Naturally, bright sunlight is more effective. 

With adequate protection of personnel against stray radiation, a solution of 400 mg of trans-p,p -azotoluene in 100 ml of petroleum ether is subject to the radiation from an unshielded quartz mercury lamp for 30 min at a distance of 30 cm. 

Trifluoronitrosomethane (b.p. 86.0°C, 767 mm Hg) is of considerable interest as a component of high temperature-resistant elastomers. This compound has been prepared by treatment of trifluoroiodomethane, in the presence of mercury, with nitric oxide in a photochemical reactor whose mercury lamp emitted radiation at 253.7 mp.. The preparation is particularly sensitive to the initial pressure of the gases, reactant ratio, irradiation time, intensity of the ultraviolet radiation, reaction temperature, and method of removal of nitric oxide from the product [60]. 

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