Reflectance-absorption spectroscopy, See

IRRAS Infrared reflection absorption spectroscopy, see also ... 

The infrared spectroscopy has been used largely in Surface Science to study adsorbed molecules on surfaces in vacuum. The infrared beam is reflected at the crystal surface and the adsorbed molecules interact with the incident light [1, 2). Greenler proposed the basic principles of the reflection-absorption spectroscopy in 1966 [3]. From his work, it becomes clear that the light interacting with the adsorbed molecules on a metal surface is only the parallel mode of the electric field of the incident radiation. This leads to the sosurface selection rule, a central concept in reflection-absorption spectroscopy (see Sect. 3.4.2.1.2). 

Infrared drying, ceramics processing, 5 656 Infrared dyes, 9 500 Infrared emission spectroscopy, 23 142 Infrared inks, 14 315 Infrared lasers, 22 180 Infrared LEDs, 22 175, 176 Infrared measurements, in growing amorphous silicon, 22 130 Infrared microspectroscopy, 16 486 Infrared reflection-absorption spectroscopy (irras), 24 72, 114-116. See also IR spectra... 

Ir spectra, of surface layers, 24 110. See also Infrared reflection-absorption spectroscopy (IRRAS) ir spectrometers, 23 132 Ir (infrared) spectroscopy, for analysis of MF resins, 15 790. See also Infrared technology Isanic acid, 5 34t... 

Generally, the assumption is made that scattering does not depend on the wavenumber so that the conversion of the measured reflectance spectrum R by means of the Kubelka-Munk function F R), results in an absorption-proportional representation. As for ATR and reflection-absorption spectroscopy, also the diffuse-reflectance spectmm does not consist of dispersion features but band-like structures. For changes in low absorption, the sensitivity of diffuse reflectance is greater than the one of transmittance, while strong absorption bands are less pronounced in the diffuse-reflection (see Fig. 6.4-18). Therefore, diffuse-reflection spectra resemble poorly resolved transmittance spectra. For diffuse reflectance spectra where R is in the order of 0.01 or below, the function -log R or just I / R is equally well suited for conversion (Olinger and Griffiths, 1988). Such level are found with compact samples such as polymer foams or varnishes with filler (Otto, 1987 Korte and Otto, 1988). 

Information on the conformational state of the hydrocarbon chains and their orientation has been obtained from external infrared reflection absorption spectroscopy (IRRAS). The first systematic IRRAS studies on phospholipid Langmuir monolayers were reported by Dluhy et al ) (see, for instance fig. 3.62). For DPPC monolayers in the LE phase the positions of the conformation-sensitive symmetric and anti-symmetric C-H stretching bands in the IRRAS spectra were found to be at the same positions as for bilayer systems of DPPC above the Kralft temperature. In the LC phase the frequencies of these bands indicate that the hydrocarbon chains of the lipid molecules are in the all-trans ) conformation (i.e. zig-zag) and analysis of polarized IRRAS spectra show that their average tilt is ca 35° relative to the monolayer normal. This is in reasonable agreement with the tilt angle of 30° obtciined from X-ray diffraction on DPPC monolayers (30°). 

The FTIR spectrum of the PTFE film deposited by laser ablation was identical to that of the target [54], but that of the film produced by SR etching showed some visible differences (see Fig. 29). Obviously, the C-F2 deformation bands at 640 and 513 cm-1 appear much smaller in the bottom trace. To understand why these 640 and 513 cm-1 bands were so small in the SR case, we measured both normal and oblique transmission of FTIR with an incident angle of 0 and 80° [58]. Two FTIR spectrometers (PERKIN-ELMER and JASCO) were used to measure spectra in the range 400-3000 cm-1. For a cross-check, the film was also deposited on a metallic surface and infrared reflection absorption spectroscopy [62] was carried out to confirm our oblique transmission measurements. Typical changes in the FTIR transmission... 

Infrared reflection absorption spectroscopy (polarization modulated spectroscopy with a dispersive spectrometer) has been used in studies of the kinetics of the formation of CuSCN multilayer Aims [248]. An advantage of this method— absolute spectra showing no differential bands, which are difficult to interpret— became obvious in a study of CO adsorption on platinum [222]. With the various neutral electrolyte solutions that are used, significant differences were observed in the results obtained with acidic solutions. The mode of CO adsorbed in the bridged position grows considerably in intensity and the position of the on-top COad is slightly shifted (see Fig. 5.56). 

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