Infrared window materials, transmission

Fig. 9 Structure and infrared absorption bands correlation chart. Transmission ranges for infrared window materials Csl, KBr, ZnSe, KRS-5, Baf2, Cap2, and NaCl are also indicated on the chart. (From Perkin-Elmer Corporation.)...

Transmission Fourier Transform Infrared Spectroscopy. The most straightforward method for the acquisition of in spectra of surface layers is standard transmission spectroscopy (35,36). This approach can only be used for samples which are partially in transparent or which can be diluted with an in transparent medium such as KBr and pressed into a transmissive pellet. The extent to which the in spectral region (typically ca 600 4000 cm ) is available for study depends on the in absorption characteristics of the soHd support material. Transmission ftir spectroscopy is most often used to study surface species on metal oxides. These soHds leave reasonably large spectral windows within which the spectral behavior of the surface species can be viewed. 

An important consideration in the choice of infrared cells is the type of. window material to be used. The material must be transparent to the incident infrared radiation and thus alkali halides are normally used in transmission methods. The cheapest material is sodium chloride (NaCl), with other commonly used materials being listed in Table 3.2a. ... 

In this section, applications will be discussed which illustrate the versatility and advantages of CVD diamond as an infrared and multi-spectral window material. We describe the use of CVD diamond optical elements including CVD diamond domes and flat plates as windows for IR seekers or imaging systems in high-speed flight or other mechanically aggressive environments. Then we describe the use of CVD diamond windows for the transmission of high-power IR laser beams. 

High-pressure sodium vapor lamp Lighting tube, special-purpose lamp, infrared transmission window materials Laser materials... 

Many polymer products exist as viscous liquids. A simple and convenient method for such nonvolatile materials is to produce a capillary film between a pair of transmission windows. If the material is very viscous, another approach is to form a thin-smear film on a single window. If the sample is extremely viscous, such as a tar or a resinous material, it is possible to dissolve the sample in a suitable volatile solvent, and evaporate a film of the material from solution onto the surface of a single infrared window. This approach may also be used for solid polymers that are easily dissolved in a... 

Cells for holding samples, or windows within the spectrometer must be made of infrared transmitting material. Table 2.1 lists approximate low wavenumber transmission limits for some optical materials used in infrared spectroscopy. All the materials listed transmit in the mid-IR above the transmission limit except for polyethylene, which is used below 600 cm" only, as it has absorption bands at higher frequencies. The transmission limits are not sharply defined and depend somewhat on the thickness of the material used. For example, a typical cell for liquid samples which is made of NaCl... 

Infrared optics is a fast growing area in which CVD plays a maj or role, particularly in the manufacture of optical IR windows. 1 The earths atmosphere absorbs much of the infrared radiation but possesses three important bandpasses (wavelengths where the transmission is high) at 1-3 im, 3-5 im and 8-17 pm. As shown in Table 16.2, only three materials can transmit in all these three bandpasses single crystal diamond, germanium, and zinc selenide. 

The following table lists the more common materials used for optical components (windows, prisms, etc.) in the infrared region of the electromagnetic spectrum. The properties listed are needed to choose the materials with optimal transmission characteristics.1 2 The thermal properties are useful when designing experiments for operation at elevated temperatures.3-5 This listing is far from exhaustive, but these are the most common materials used in instrumentation laboratories. 

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