Attenuated multiple total internal reflection

The second case refers to the so-called Internal Reflection Spectroscopy, that is used in the so-called Attenuated Multiple Total Internal Reflection technique... 

The formulation of a sulfur-vulcanized styrene-butadiene rubber (R2) mainly contains the rubber polymer and precipitated silica as filler the rest of the components are minor in amount, but they are important to impart adequate vulcanization and protect the rubber from the degradation under use (mainly paraffin wax). The paraffin wax acts as a physical protecting agent against ozone by migration to the rubber surface (Romero-Sanchez and Martin-Martinez 2004). O Figure 43.6 shows the attenuated multiple total internal reflection-infrared spectroscopy (ATR-FTIR) spectrum of the R2 bulk. The main bands correspond to rubber (styrene and butadiene) and silica, and the presence of CH2 moieties are minor corresponding to the paraffin wax. However, the ATR-FTIR spectrum of the R2 surface shows the main bands due... 

The main problem in IR measurements in situ is a strong IR absorption by the solvent water. Therefore the measurements in the classical transmission mode are practically excluded (the path length must not exceed 15 tan). Short path lengths are provided by the attenuated total reflection (ATR) mode. The probing light beam undergoes multiple total internal reflection in the ATR element (e.g. a cylindrical rod made of ZnSe, with two cone-sharpened ends) and each reflection... 

Infrared spectra can also be obtained by reflecting the IR beam on the surface of a sample. This technique is applied when it is not possible to obtain an IR spectrum by a transmission technique. Attenuated total reflectance (ATR) also known as ATIR (attenuated total internal reflectance) is based on multiple internal reflectance of the IR beam on the sample surface using a high refractive index crystal (e.g.. 

Attenuated total reflection (ATR) has grown into the most widely practiced technique in infrared spectrometry. The reasons for this are fairly straightforward the technique requires little or no sample preparation, and consistent results can be obtained with relatively little care or expertise. The technique is not foolproof, but it can be very forgiving. ATR spectrometry is known by a number of alternative names, for example, multiple internal reflection (MIR), which is not to be confused with mid-infrared, frustrated multiple internal reflection (FMIR), evanescent wave spectrometry (EWS), frustrated total internal reflection (FTIR), which is not the same as Fourier transform infrared (FT-IR) spectrometry, and internal reflection spectrometry (IRS), but IRS is better known, at least in the United States, as the Internal Revenue Service. 

If the sample is placed in good contact with the surface of an optical device of high refractive index (such as a prism of KRS-5) and illuminated through the prism by IR, the beam passes into the layers in contact and is attenuated before being totally internally reflected by the system, as shown in Figure 5(b). This is called attenuated total reflectance or ATR. If the beam interacts several times, then we have multiple internal reflectance (MIR) and if the surface is horizontal, which is an advantage in setting up the sample, then it is horizontal attenuated total reflectance (HATR). 

The surfaces of infrared-transparent materials that are available in the form of shaped and polished crystals, such as silicon or germanium, can be studied with good sensitivity by using attenuated total internal reflection (ATR) in conjunction with multiple reflection procedures. 

Southern England. Changes produced by such a short exposure are not apparent from conventional multiple attenuated total internal reflectance i.r. studies but are readily detected by ESCA as will become apparent. 

Solid state spectra can be measured by the Attenuated Total Reflectance or Multiple Internal Reflection methods as well as by simple transmission techniques (222). Brooker (223) has reported the discovery of the translational vibrations of NaN02, NaNOs, and CaCOs (calcite). The orientation of the bonds in (U02)(N0s)2. 6 H2O has been ascertained from the spectra obtained in this manner (223). 

The most commonly used technique for obtaining a spectrum is the attenuated total reflectance (ATR) method in the multiple internal reflectance (MIR) mode. In this method, the infrared beam is passed into a special crystal of a selenide (KRS-5). The angle of incidence is such that the beam will bounce along the crystal. A sample of the polyurethane is placed hard up against the crystal. The infrared just penetrates into the material before it continues down the crystal. A number of internal bounces are obtained along the crystal. Up to 25 reflectances are obtained from a 2 mm crystal. Figure 9.8 illustrates the infrared path in an ATR cell. 

Diffuse Reflectance, Attenuated Total Reflection or Multiple Internal Reflection, Photoacoustic (PAS), Photothemal Beam Deflection, Specular Reflection Absorption, and forensic applications with the diamond cell and the Fourier transform infrared (FTIR) microscope. In museum laboratories, FTIR applications have been used for problems of identification and degradation in art and archeology. (14)... 

IR spectroscopy is a common analytical technique in the textile industry. IR is capable of identifying fibers and their additives, as well as showing quantitative blend ratios and additive contents. The ATR (attenuated total reflection) technique, especially in its multiple form, MIR (multiple internal reflection) is of special importance in this field. The sample preparation is simple and fast the cut out swatches with appropriate surface areas are placed against each side of the MIR crystal, ensuring sufficient and uniform contact across the crystal surface. The internal reflection methods are non-destructive, so that the sample may be saved for other types of analysis, they are, further, methods of surface analysis. This is advantageous in all cases where the finish resides primarily on the fiber surface. In this case, a very strong spectrum of the finish is obtained, with minimal interference from the base fiber (Hannah et al., 1975). 

The sample absorbs the evanescent field so that the totally reflected wave is attenuated accordingly the reflectance spectrum closely resembles a transmission spectrum. Usually such spectra can actually be inteipreted and evaluated as transmittance, and commercially available accessories are designed to support this. With angles of reflection well above the critical one, some sensitivity is lost which however is regained by multiple internal reflections. How pronounced the actual spectrum is, can be adjusted by the number of reflections used, i.e. the sample-coated area of the slab whether both surfaces, one surface, or just a fraction. In any case the area of a given reflection should fully be covered to avoid spectral dilution. 

Adsorption of CN on a silver metal film was reported by Hatta et al. [112], using multiple internal reflection in an ATR (attenuated total reflection) prism configuration. Basically the same features were observed by Hatta et al. as in the external reflection approach, namely a potential-dependent band located between 2100 and 2118 cm assigned to the adsorbed CN ion and another band located at 2143 cm , assigned to the Ag(CN)2 complex. The feature at 2167 cm was not observed, because of the limited potential range used in this experiment to avoid the dissolution of the silver film [112]. 

Another approach, internal reflection spectroscopy (IRS) or attenuated total reflectance (ATR) spectroscopy, takes advantage of the total reflection observed when a light beam is directed to the back of the OTE at an angle greater than the critical angle. Since the reflection takes place at the electrode-solution interface, the light beam is attenuated only by molecules close to the electrode surface. The penetration depth is about 1000 A in a typical experiment. Because of this very small effective cell length, the electrode is most frequently used in a multiple reflection mode [Fig. 44(b)]. 

A nonelectrochemical method also sensitive to the presence of water is infrared spectroscopy with multiple internal reflection, applied by Nguyen and coworkers to study the swelKng of an organic coating at the metal-polymer interface in situ [58]. The integration of the stretching vibration of water was used as a measure of the water uptake at the interface. Stratmarm and coworkers measured the increase of the water concentration at the Fe-alkyd-polymer interface by means of single attenuated total infrared reflection spectroscopy (ATIRS) [59]. An ultrathin Fe film was evaporated onto a ZnSe crystal and coated with an alkyd primer. The authors concluded that no separate water film is... 

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