IR transmission windows

The most basic samphng device is the IR transmission window see Table 1 for a summary of common IR transmitting materials. This is primarily used... 

Repeated attempts to obtain the band at 1030 cm 1 in spectra of the respective solids of various compositions did not furnish the desired result. Nevertheless, the band was observed in IR transmission spectra of gaseous components that separated from molten K2NbF7 and were collected in a standard gas phase cell with Csl windows appropriate for IR measurements. Fig. 85 presents the structure of the band and exact wave numbers of its components. Storage of the gas in the cell for several days resulted in a yellow deposit on the windows due to oxidation and subsequent separation of iodine. Analysis of available reported data [364 - 367] enables to assign the band observed at -1030 cm 1 to vibrations of OF radicals. It should be emphasized that a single mode was observed for OF in the argon matrix while in the case of nitrogen, two modes were indicated [367]. 

In solvent-elimination LC-FTIR, basically three types of substrates and corresponding IR modes can be discerned, namely, powder substrates for diffuse reflectance (DRIFT) detection, metallic mirrors for reflection-absorption (R-A) spectrometry, and IR-transparent windows for transmission measurements [500]. The most favourable solvent-elimination LC-FTIR results have been obtained with IR-transparent deposition substrates that allow straightforward transmission measurements. Analyte morphology and/or transformation should always be taken into consideration during the interpretation of spectra obtained by solvent-elimination LC-FTIR. Dependent on the type of substrate and/or size of the deposited spots, often special optics such as a (diffuse) reflectance unit, a beam condenser or an FITR microscope are used to scan the deposited substances (typical diameter of the FITR beam, 20 pm). 

HP IR transmission cells can be divided into two broad categories, namely (i) where the contents of the high pressure vessel are observed directly through IR transparent windows and (ii) where the reaction solution is circulated from the autoclave to an auxiliary observation cell. The first type is exemplified by the cell shown in Figure 3.2, developed by Whyman at ICI [2, 3]. The stirred reaction solution surrounds the cell windows in an arrangement that minimises the problem of... 

Fig. 17. Cross-section of the view cell at the spectroscopic level. The IR beam is directed either through the ATR crystal (bottom, solid lines) or through the transmission windows (upper part, dashed lines). The four mirrors are mounted on a motor-driven mobile attachment (76).

FTIR Microspectroscopy.3 A microscope accessory coupled to a liquid-nitrogen-cooled mercury-cadmium-telluride (MCT) detector can be used to obtain an IR spectrum. This is possible in both the transmission and reflectance modes. Several beads are spread on an IR-transparent window (NaCl, KBr, diamond) and possibly flattened via a hand-press or a compression cell. The IR beam is focused on a single bead using the view mode of the microscope. The blank area surrounding the bead is isolated using an adjustable aperture, and a spectrum is recorded using 32 scans (<1 min). A nearby blank area of the same size on the IR transparent window is recorded as the background. 

Cocondensation of sublimed samples of M(TPP) (M = Ru, Os) with dioxygen on a CsCl window in vacuo and subsequent IR transmission spectroscopy at 30 K of the films thus produced served to identify p-peroxobis-[porphyrinatometal(III)] species for both metals. Additionally, for M = Ru, the pentacoordinate end-on adduct Ru(02XTPP) was also identified [259]. Its pyridine adduct, Ru(02XTPP)Py, was already observed in the previous study [258],... 

IR spectroscopy was mainly used to characterize the sorbed species. The zeolite powder was pressed into self supporting wafers and analyzed in situ during all treatments (i.e., activation, sorption, reaction) by means of transmission absorption IR spectroscopy using a BRUKER IPS 88 FTIR spectrometer (resolution 4 cm" ). For the sorption experiments, an IR cell equipped with IR transparent windows which could be evacuated to pressures below 10" mbar was used [11]. The activated zeolite wafer was contacted with a constant partial pressure (0.001 mbar) of the adsorbate at 308 K until adsorption-desorption equilibrium was reached (which was monitored by time resolved IR spectroscopy). For the coadsorption experiments, the catalysts were equilibrated with 0.001 mbar of both adsorbates admitted in sequentional order. The spectra were normalized for the sample thickness by comparing the intensities of the absorption bands of the adsorbate with the integral intensity of the lattice vibration bands of the zeolite between 2090 and 1740 cm". The surface coverage was quantified by calibration with gravimetric measurements (under conditions identical to the IR spectroscopic experiments). 

In the near future this work will shift to lower and more easily accessible redshifts near z = 2.2 where all the lines of interest, from [O II] A3727 to Ha, fall in near-IR atmospheric transmission windows. Nevertheless, the determination of element abundances from nebular emission lines will remain a time consuming task until multi-object spectrographs... 

Possibly the best way to obtain transmission spectra from hydrogels is to prepare a capillary thin film onto a water-insoluble and IR-transparent window. The preparation of capillary films is simple a drop or smear of the hydrogel sample is placed onto the window and a second window is placed on the top of the first. The resulting sandwich is placed in the IR beam. 

Krell A, Baur G, Dahne C (2003) Transparent sintered sub-pm AI2O3 with IR transmissivity equal to sapphire. In Tustison RW (ed) Window and dome technologies VIII. SPE-Int Soc Optical Engineering, Bellingham, pp 199-207... 

Deposition of analytes in solvent-elimination LC-FTIR is performed on powdered substrates, mirrors, or IR-transparent windows. Correspondingly, diffuse reflection Fourier-transform infrared (DRIFT) detection, reflection-absorption (R-A) spectroscopy, or transmission measurements are applied to investigate the analyte deposits. 

Vibrational spectroelectrochemical techniques, particularly Fourier transform infrared (FTIR), with the advent of less-expensive and more sensitive spectrometers, have enjoyed a great increase in popularity over the last few years. The advantages over UV-vis spectroscopy include greater specificity and enhanced information content. An IR OTTLE transmission cell with IR-transparent windows can be built by modifying a commercial liquid cell. Raman spectroscopy is also very easily carried out with an OTTLE cell, but a flow cell is more useful for SERS studies of adsorption, since the solution can be replaced without disturbing the optical alignment. 

This calcium aluminate fiber was evaluated in structural applications but it was not suitable for the evaluation of infrared optical properties because it contained bound water as evidenced by a strong hydroxyl band at 29 jjm in the IR transmission spectra. Hydroxyl-free compositions were made in carbon crucibles [17] by the Davy process [39], i.e., by a procedure [40] by which disposable optical calcium aluminate bulk glasses are prepared for commercial applications in optical windows. 

Transmission. The transmittance of glasses is limited by electronic excitiations and light scattering in the UV, by vibronic excitations in the IR, and by reflections and impurity absorptions within the transmission window (in the visible part of the spectmm) Fig. 3.4-27. The UV absorption edge is temperature dependent. An example is shown in Fig. 3.4-28. 

The transmission window of ChG glasses overlaps the 400-4,000 cm IR range, which corresponds to the region of vibrational modes of organic species. This makes ChG-based FEWS an excellent tool for remote detection and analysis of a wide variety of chemicals and biochemical compounds. In this section we will review the advances and main applications of the FEWS technology, ranging from the detection of simple molecules to the detection of complex proteins and enzymes. 

Contemporary infrared (IR) systems for the free-space optics (FSO) in the wireless last-mile access, private networks and mobile infrastructure applications mostly utilize the transmission window 0.7-1.55 pm which is very sensitive to some influences of atmosphere. Rain, fog, smoke, dust particles effectively shorten the available range in this window. Typical fog drops have dimensions comparable to the operating wavelengths, and the resulting real-Ufe maximum distances are typically below 200-300 m, although distances of a few kilometers have been achieved in favorable conditions in point-to-point systems [407]. 

High-purity spinel is a chemically derived spinel powder made hy the co-precipitation of magnesium and aluminum complex sulfates, with subsequent calcination to form the oxide compound. Purities range from 99.98-99.995%. Since it is chemically derived, the stoichiometries can he adjusted for virtually any MgOiAljOj ratio. The ceramic powders prepared hy this process can he hot pressed into transparent window materials with exceptional IR transmission range. 

While inspecting equipment through an IR transmitting window, the transmission loss through the window as well as the thermal contribution of the window itself should be considered. If measurement accuracy is critical, the data furnished with the window can be used to correct the measurement. 

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