Xenon light source

The ellipsometer used in this study is described elsewhere(3). It consists of a Xenon light source, a monochromator, a polarizer, a sample holder, a rotating analyzer and a photomultiplier detector (Figure 1). An electrochemical cell with two windows is mounted at the center. The windows, being 120° apart, provide a 60° angle of incidence for the ellipsometer. A copper substrate and a platinum electrode function as anode and cathode respectively. Both are connected to a DC power supply. The system is automated with a personal computer to collect all experimental data during the deposition. Data analysis is carried out by a Fortran program run on a personal computer. 

As mentioned in sections 1.2.2.2 and 1.2.3.2, the photochromic reactions of spirobenzopyran and spironaphthoxazines show a marked solvent dependency and this is also the case with benzo and naphthopyrans. Consequently, spectral data collected from the literature is only comparable within any one study or where the same solvent has been used. This accounts for any discrepancies between one set of results and any other one listed in this and related sections of this chapter. The data normally quoted when discussing the properties of photochromic materials relate to the absorption maximum (2. ) of the coloured state, the change in optical density (absorbance) on exposure to the xenon light source (AOD) and the fade rate which is the time in seconds for the AOD to return to half of its equilibrium value. 

Aqueous photolysis t,/2 = 6.3 h in pH 5 sterile buffer solution soil photolysis t,/2 = 14.2 d in air-dry sandy loam soil when exposed to a xenon light source air photolysis t,/2 = 2 h when exposed to a light source simulating summer sunlight at 34°C (Wolt 1997). 

In spectrophotometric analyzers, interference filters are selected for desired wavelengths, as determined from the spectral relationship curves. Photodetectors are least sensitive in the blue end of the spectrum. This can be dealt with by using prefilters or narrow spectral ranges, which are calibrated for more sensitivity. Improvements in spectrophotometers include a flashed xenon light source with dual-beam measurement. Dual-beam machines measure the spectrum of both the light source and the reflected light for each measurement. 

Few instances of companies in the United States using xenon light sources were reported. 

Fluorometers and fluorescence spectrophotometers are available that offer a variety of features. These features include ratio referencing, microprocessor-controlled excitation and emission monochromators, pulsed xenon light sources, photon counting, rhodamine cell for corrected spectra, polarizers, flow cells, front-surface viewing adapters, multiple cell holders, and microprocessor-based data reduction systems. 

The Xenotest is manufactured in two versions by Quartzlampen Gesellschaft (Hanau, Germany). The model 150 incorporates a 1500 W air-cooled xenon light source, while the model 450 uses a 4500 W air-cooled unit. Because of the ozone produced by the air cooled lamps, Xenotests should be vented directly to the outside. In the Xenotest 450, temperature is controlled by a system similar to that of the Atlas machines. Fresh air is blown through the model 150 but the temperature is not regulated. Humidity control is obtained automatically by the use of spray nozzles which atomize water into an air stream. Rainfall can be simulated by a water spray directed at the samples. 

We have modified a 1 kW Oriel xenon light source to provide an 8 inch illuminated circle with light between 300 and 1,000 nm to simulate sunlight for our prototype device. We have measured the light intensity distribution in the circle so that we can correct for effects of non-uniformity in the light field on the performance of photocatalysts. 

FIGURE 64 Development of surface cracks on PP surfaces on exposure to a filtered xenon light source (600W/m ) at 42°C and at different durations of exposure. Source Reproduced with permission from Yakimets et al. (2004). 

B) (a) FP-TRMC profile of the 2D D-A COF in Ai (black) and SF6 atmospheres (blue), (b) Accumulated number of photo-induced charge carriers in the 2D D-A COF upon 355 nm pulse exposure, (c) I-V curve of the 2D D-A COF in the dark (black) and upon irradiation (red) with visible light from a Xenon light source, (d) Photocurrents of the 2D D-A COF (red curve), COF-5 (black), and a simple mixture of D and A at a molar ratio of 3 2 (blue) upon repeated switching of the light on and off. 

The collimated xenon light source iUuminated 20% of the chamber volume. After correcting for total percent chamber illumination, estimated rates of photolysis were found to be comparable to those reported by Woodrow et al. (S) and Monger and Miller (7) who conducted stable tracer trifluralin photochemical evaluations under outdoor sunlight conditions. 

Pandey, K.K., Vuorinen, T. Comparative study of photodegradation of wood by a UV laser and a xenon light source. Polym. Degrad. Stab. 93(12), 2138-2146 (2008)... 

The magneto-optical properties of the y-Fe203 nanocomposites were measured by embedding blocks of the material inside an acrylic resin and polishing until plates are obtained with a thickness ranging from 0.2 to 1 mm. The experimental setup to get the Faraday rotation spectrum is based on a Xenon light source, a monochromator (with a resolution of 1 nm), an optical power meter, two near-infrared (IR) polarizers with their axes at 45°, and an electromagnet with tapered... 

The chemical durability of a composite resin can be tested by accelerated aging in a weathering chamber (6). Disks (36 mm in diameter and 1.3 mm thick were exposed to conditions of accelerated aging for a total of 900 hours in a weathering chamber at 43 C and 90 percent relative humidity. One surface of a sample was subjected continuously to the radiation of a 2500 watt Xenon light source filtered by borosilicate glass and to an intermittent water spray for 18 minutes every two hours. Changes in the exposure surface were studied by surface profile measurements and by SEM. 

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