Window material

Most samples to be investigated by mid-infrared spectrometry, except polymer films and KBr pellets, must be held between two windows. Glass cannot be used as a window material in the mid-infrared, and salt plates are used instead. The two most important properties of the materials that are used for infrared spectrometry are the cutoff and the refractive index these parameters are listed in Table 11.1. 

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Here, the wavelength of the laser light is A, and is a correction term due to the wavelength dependence of the refractive index of the etalon material ( = 0.034 at 514.5 nm when fused silica etalons are used to achieve the necessary delay, or = 0 when a lens combination is used). The optical correction term Av/v results from the change in refractive index of the window material with shock stress (Barker and Hollenbach, 1970). If the measure-... 

Impact of a thin plate on a sample of interest which is, in turn, backed by a lower impedance window material leads to an interaction of waves which will carry an interior planar region into tension. Spall will ensue if tension exceeds the transient strength of the test sample. A velocity or stress history monitored at the interface indicated in Fig. 8.4 may look as indicated in Fig. 8.5. The velocity (stress) pull-back or undershoot carries information concerning the ability of the test material to support transient tensile stress and, with appropriate interpretation, can provide a reasonable measure of the spall strength of the material. 

Type Origin Spectral Wavelength maximum sensitivity Window material... 

Fig. 3-5. Attenuation of a polychromatic beam by various materials. Note superiority of beryllium as a window material. (Liebhafsky, Smith, Tanis, and Winslow, Anal. Chem19, 861.)...

The most common IR window materials are zinc sulfide, which is translucent, and zinc selenide, which is transparent. Both of these materials are made by low-pressure CVD by the reaction of vaporized zinc and hydrogen sulfide or selenide (see Ch. 12). Germanium, another common IR window material, is also produced by CVD (see Ch. 8). 

Phosphorus-containing pesticides la 254 Phosphorus insecticides lb 83 Phosphorus pesticides lb 32 Photochemical activation lb 13 Photochemical reactions lb 15,17 Photodiodes la 24,29 Photo effect, external la 24 -, internal la 24, 29 Photo element la 24,29 Photography, exposure times la 137 -, instmmentation la 137 Photomultiplier la 25ff -, disadvantages la 27 -, energy distribution la 26 -, head on la 27 -, maximum sensitivity la 28 -, side on la 27 -, spectral sensitivity la 28 -, window material la 28 Photocells la 25 Phloxime lb 116... 

Internal heat exchange is realized by heat conduction from the microstructured reaction zone to a mini channel heat exchanger, positioned in the rear of the reaction zone [1,3,4], The falling film micro reactor can be equipped, additionally, with an inspection window. This allows a visually check of the quality of film formation and identification of flow misdistribution. Furthermore, photochemical gas/liquid contacting can be carried out, given transparency of the window material for the band range of interest [6], In some cases an inspection window made of silicon was used to allow observation of temperature changes caused by chemical reactions or physical interactions by an IR camera [4, 5]. 

XRF has also been hyphenated to various chromatographic techniques, cf. TLC-XRF (Section 7.3.5.1). For process XRF, the stream interface is a simple by-pass flow the window material that allows the X-rays to enter the product stream-a thin film of polycarbonate-confines pressure and temperature. 

Most recently, they have developed" a cell configuration for the study of modified electrodes that employs, as a working electrode, colloidal graphite deposited onto kapton tape (typically employed as a window material). Such an arrangement minimizes attenuation due to the electrolyte solution. 

Beryllium metal is used as a window material for X-ray tubes (it has 17 times the transmittance of aluminum). Notwithstanding the high cost of the metal, it has been tested for use in high-performance sports equipment such as golf clubs, bicycles, and motorcycles. 

The reactor assembly was heated by electric heaters. The maximum operating temperature Is determined by the window construction. Sapphire windows (from EIMAC), brazed into Kovar sleeves, were used the sleeves were then welded directly into the stainless steel reactor housing. We found that the cell so constructed was capable of trouble-free, continuous operation at 450°C operations at somewhat higher temperatures are probably still possible but were not explored. Sapphire was chosen as a window material because it is insensitive to water vapor and is transparent in tljie wave number range of our interest (about 2400 cm to 2000 cm in these experiments). Moreover, the thermal expansion characteristics of the reactor were found to match well with those of the window fixture. 

Window insulation, noble gases in, 17 378 Window material, in ir cells, 14 228-229 Windows... 

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