The ATR properties

Fig. 4 shows the ATR properties of the Ag sputtered films measured using He-Ne laser beam of the wavelength at 632.8 nm. The closed circles represent experimental data and the solid lines represent calculated ones. The theoretical calculations of the ATR curves were carried out from Fresnel s formula using transfer matrix method [20]. The dielectric constants and the film thicknesses obtained by curve fittings are 38.05 nm and -17.017+i 0.595 for sample A and 38.51 nm and -17.523+i 0.704 for sample B, respectively. 

The ATR properties of the MC LB film measured at 488,0 nm are shown in Fig. 8. The MC LB films were deposited on the evaporated Ag thin films covered with 2 monolayers of C20Cd LB films. MC4L and MC8L in the figure indicate the results for the MC LB films with 4 and 8 monolayers, respectively. The ATR property of the Ag thin film is also shown in Fig. 8. 

The short-circuit photocurrents (Isc) were investigated for the MC LB photoelectric cell in the ATR configuration. The Isc profiles as a function of the incident angle corresponded to the ATR properties in the cell. From the calculations, it was estimated that the Isc was caused by strong optical absorption in the cell related to the SPP excitations. 

It is therefore unnecessary to alter the chemical properties of the bulk material, e.g. by using vapor phase deposition of sensitizer and monomer. This can be seen by comparison of ATR-IR and ESCA spectra of grafted PP surfaces (Figure 3). 

Many compounds exhibit near-IR and mid-IR absorption. By using IR transparent optical fibers, detection of an absorption band in the IR region is possible for optical sensing. Both direct sensing using the absorption property of the analyte or indicator sensing are widely exploited. Most mid-IR sensing schemes are based on the principles of internal reflection spectroscopy, or the attenuated total reflection (ATR) [3,14-21],... 

In recent years, research on catalysts for the ATR of hydrocarbons has paid considerable attention to perovskite systems of general formula ABO3. In the perovskite stmcture, both A and B ions can be partially substituted, leading to a wide variety of mixed oxides, characterized by structural and electronic defects. The oxidation activity of perovskites has been ascribed to ionic conductivity, oxygen mobility within the lattice [64], reducibility and oxygen sorption properties [65, 66]. 

There are few reported analyses of the thermodynamics of carbon deposition in the ATR of liquid fuels. Though typically not stated in these analyses, the calculations were presumably carried out using the thermodynamic properties of elemental carbon e.g., as formed in reactions (6)-(8) above), rather than any coke species (which consist of a wide range of polynuclear aromatic compounds with quite different thermodynamic properties). This is an important difference, since the results apply only to elemental carbon, not coke deposition in general. 

This latter interpretation would mean that with the approach depicted in Fig. 10, the catalyst itself could be monitored. The authors reported that the silica-supported Nafion could not be observed in the beginning of their experiments and appeared in the spectra only after the catalyst interacted with octanol. This observation may indicate that the octyl groups promote the sticking of the catalyst particles onto the ATR probe, within the evanescent field. However, the example also shows that this approach may not be without problems, because it depends on the adsorption of the particles from the slurry reactor onto the ATR element. This process is accompanied by the adsorption of molecules on the catalyst surface and complicates the analysis. More important, as also indicated by the work of Mul et al. (74). this adsorption depends on the surface properties of the catalyst particles and the ATR element. These properties are prone to change as a function of conversion in a batch process and are therefore hardly predictable. 

Infrared spectra are generally temperature dependent as the observed vibrations of the molecules in the liquid phase depend on the temperature. Additionally, the effective thickness of the ATR sample depends on physical properties that may vary with temperature. Consequently, IR-ATR measurements should be carried out at constant temperature. 

Fluctuations in the dielectric properties near the interface lead to scattering of the EW as well as changes in the intensity of the internally reflected wave. Changes in optical absorption can be detected in the internally reflected beam and lead to the well-known technique of attenuated total reflectance spectroscopy (ATR). Changes in the real part of the dielectric function lead to scattering, which is the main topic of this review. Polarization of the incident beam is important. For s polarization (electric field vector perpendicular to the plane defined by the incident and reflected beams or parallel to the interface), there is no electric held component normal to the interface, and the electric field is continuous across the interface. For p polarization (electric field vector parallel to the plane defined by the incident and reflected beams), there is a finite electric field component normal to the interface. In macroscopic electrodynamics this normal component is discontinuous across the interface, and the discontinuity is related to the induced surface charge at the interface. Such discontinuity is unphysical on the molecular scale [4], and the macroscopic formalism may have to be re-examined if it is applied to molecules within a few A of the interface. 

IR radiation is emitted from the electrically modulated light source. The analytically relevant spectral range is transmitted through an interference filter, the sample chamber, and the membrane. This radiation is focused on a thermal detector (Dl), pyroelectrical or thermopile. The reflected radiation from the filter is used as a reference (D2). A comparison of the ATR-, the fiber-, and the transmission-method. Secs. 6.5.2.1, 6.5.4.2, and 6.5.4.4, shows that the ATR method is most versatile for all applications and that the transmission method allows the lowest limit of detection for gases (Hadziladzaru, 1994). The properties of the ATR method by employing wavelength selection with tunable interference filters has been studied by Lebioda (1994). 

Protein-lipid interactions and particularly peptide-lipid interactions have been studied in supported bilayers by attenuated total reflection (ATR) FTIR spectroscopy. A slightly dated, but still valid comprehensive review on this method applied to supported bilayers has been published (20). Because IR light probes the vibrational properties of different classes of covalent bonds, this method is useful to examine lipids, peptides, and interactions between the two in the same sample. The most common parameter for assessing lipid structure and order is to study the stretching vibrations of the lipid acyl chains, for example as a function of peptide concentration or temperature. Such studies have lead to the conclusion that fusion peptides from viruses increase the lipid chain order of fluid phase bilayers and that... 

The transport properties of the membrane were measured by using a membrane permeation unit as described in our previous papers.32 42 Two gas mixtures were used as the feed gas for the gas permeation tests one consisting of 20% C02, 40% H2, and 40% N2, and the other consisting of 1% CO, 17% C02, 45% H2, and 37% N2 (both on dry basis). The second composition was used to simulate the composition of the synthesis gas from autothermal reforming (ATR) of gasoline with air. Argon was used as the sweep gas for the ease of gas chromatography analysis. Unless otherwise stated, the feed pressure was maintained at about 2.0 atm, while the permeate pressure was set at approximately 1.0 atm. 

In an ATR imaging study, Kazarian and Chan described the behavior of polymer blends under high-pressure COj. Under these conditions and at 40 °C, initially homogeneous blends were seen to undergo a phase separation. By using this method, it was also possible to examine the influence of other gases on the material properties of polymers [17]. Likewise, in 2006, Kaun et al. demonstrated an FT-IR imaging system for the examination of a chemical reaction in a solution, and the time-resolved model reaction of formaldehyde and sulfite was also visualized [18]. 

Raman spectroscopy displays the same property as NIR regarding the intensities of vibrational bands. Raman bands are much less sensitive to H-bonds than IR bands, as seen in Ch. 4. For a long time, Raman spectra were therefore the most frequently used method to study liquid water, before the advent of ATR set-ups in IR spectroscopy. It has thus been possible to show that the band of liquid water is composed of two bands (68). Their significance has also for long been an object of discussion, but as indicated in Ch. 9, they are now seen as corresponding to two different states of rotations or librations of individual HjO molecules. 

Future work is being conducted to examine fuel processor durability, PEM cell durability on reformate, and operation of PEM fuel cells on hydrogen. The durability of fuel processor catalysts and reactor materials will be examined with real fuel blends with operation and design modified to help prevent carbon formation. This work will evaluate the fuel processor catalyst durability, carbon formation, and changes to the mechanical properties of ATR materials. PEM cell durability studies will concentrate on the operation and causes of degradation of the MEA portion of the fuel cell. 

It follows from the definitions above that for measuring the electrooptic coefficients, one should measure the index variation due to the application of an electric field. Evanescent waves coupled by the ATR method to surface plasmons or to waveguide modes have been demonstrated as useful tools for measuring electrooptical properties of NLO Langmuir-Blodgett films and NLO polymers [81-85],... 

The polymer properties in thin films are then compared with the bulk as measured by FTIR attenuated total reflection spectroscopy (ATR). A modest refractive index of the internal reflection element (IRE made of ZnSe, n=2.43 at 2000 cm ) and an incident angle of 65° - still low but well above the critical angle of total reflection - are chosen for the p-polarized light in order to obtain an information depth of several microns. Hence, the ATR spectra provide the bulk properties of the polymer sample. 

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