Germanium prism

This layer is then analysed directly by internal reflectance infra-red spectroscopy. Since there is no handling of the sample, contamination is reduced to a minimum. However, only infra-red spectral analysis is possible with this system since the material absorbed on the germanium prism is always a mixture of compounds, and since the spectrophotometer used for the production of the spectra is not a high-precision unit, the information coming from this technique is limited. While identification of specific compounds is not usually possible, changes in spectra, which can be related to the time of day, season, or to singular events, can be observed. 

Figure 2. Skin in situ spectrum recorded by touching forearm to germanium prism in horizontal attachment...

Figure 4. (1) MIR spectra of surface films of P/3BA from solvent I transferred on germanium prism (a) at surface pressure less than the plateau pressure, (b) at surface pressure greater than plateau pressure (2) MIR spectra of surface films of PpBA from solvent II transferred on germanium prism at high surface pressure...

Unfortunately, the Baier germanium prism does not collect a sufficient quantity of organic material to allow the use of chemical methods of analysis other than IR spectroscopy. There are other methods which do sample a sufficiently large area of surface, but these are for the most part devices which collect a thin layer of seawater adjacent to the interface. They are... 

To some authors, it seems to be apparent that the microlayer consists of a surface monolayer of adsorbed organic matter of thickness —20 A diluted by a vast excess, 10 —10 times as much, subsurface seawater. It should be noted that a monolayer thickness of this magnitude applies mostly to mono-layers of simple surfactants such as fatty lipids. Water-soluble surfactants of the wet variety (MacIntyre, 1974) can form monolayer films of much greater thickness, with hydrophobic parts of the molecule attached to the interface and hydrophilic parts extending by as much as —1 pm into the aqueous phase. The results of Baler et al. (1974), to be discussed shortly, show that films in a dry state on germanium prisms used for the Blodgett (1934, 1935) type of sampling method have thicknesses determined by ellip-... 

Studies by Baier et al. (1974) using the germanium prism method... 

As described in Section 3.1, Baier et al. (1974) have used a machined germanium prism to sample surface organic monolayers in the manner developed earlier by Blodgett (1934,1935) for fatty acid films. The basis of their analytical method, infrared spectroscopy by the technique of internal reflections inside the machined prisms, is only qualitative but serves very well to examine the chemical nature of the surface organics. It is well known that when an internal reflection prism made of a material with a sufficiently high index of refiraction such as germanium is used, the internal reflection IR spectrum obtained suffers no band distortion or band shift when compared to conventional transmission spectra of the same substance (Barr and Flournoy, 1969). 

The hardening of the boundary layer of epoxy and polyester compositions was studied by IR spectroscopy (of repeatedly disturbed total internal reflection—RDTIR) on a UR-20 spectrometer. A KRS-5 prism N =18, C = 45°) and a germanium prism N =14, C = 45°) were used for simulation of the substrate surface. The thickness of a polymer layer was 0.5-1 nm for the element made of germanium and 2-3 nm for KRS-5. Inhibition of polyester resin polymerization by atmospheric oxygen was eliminated by applying a polyethylene film to the surface of a system to be hardened. The thickness of the applied epoxy and polyester composition was up to 20-30 nm. To evaluate the glass-transition temperature and the polymer-solvent interaction parameter, we used reversed-phase gas chromatography. Basalt-1 and basalt-2 (see below) served as fillers and as a model substrate. The... 

The formation of rings in the pdymer chain by the pdymerization of nitrile groups has also been observed in the bulk pd3rmerization of acrylonitrile by Trifonov and Shopov. In this study of the electroinitiated pdymerization of acrylonitrile with tetraethylammonium perchlorate as supporting electrolyte, the polymer was formed on a germanium prism which was part of an internal reflection spectroscopy device. The appearance of the absorption band at 1570 cm" in the spectrum of Ae yellow colored polymer indicated the presence of conjugated multiple bonds idiich was also supported by uv absorption at a lot r wavelength 304 tun, compared to 271 nm for white polyacrylonitrile prepared by free-radical initiation. 

Arachidic acid monolayers were prepared from a benzene solution on the water subphase of pH5.8(pure water) and 12.6(adjusted by addition of NaOH) at Tsp of 303 K below Tm(=328 K) of the monolayer [31]. The ionic dissociation state of hydrophilic group was estimated on the basis of the stretching vibrations of carbonyl and carboxylate groups by Fourier transform-infrared attenuated total reflection, FT-IR ATR measurements. 70 arachidic acid monolayers were transferred on germanium ATR prism, resulting in the formation of the multi-layered film. Transfer on the prism was carried out at surface pressures of 25 or 28 mN-nr1. Infrared absorption measurements revealed that almost carboxylic groups of arachidic acid molecules did not dissociate on the water subphase of pH5.8, whereas all carboxylic groups dissociated as carboxylate ions on the water subphase of pH 12.6. 

An IR beam passing through a prism made of a material with a high refractive index n2 (germanium n = 4) under the angle of total reflection (n, < n2) is totally internally reflected. 

Saliva - Dental Materials Interactions. Besides enamel and other tissues, surfaces from metallic, polymeric, and ceramic dental materials are capable of becomimg adsorbed with organic films. Germanium and silica infrared spectrometer prisms formed oral films at high speeds and were... 

Fig. 3. Crystal structures of YbPdTl (FcjP type) and YbAgGe (ZiNiAl type). The three-dimensianal [PdTl] polyanion is outlined at the left-hand side vidiile ftie trigonal prisms around the germanium atoms are emphasized...

When using the MIR technique for the analysis of aqueous solutions, germanium is taken as the prism material (angle of incidence (3) 19 to 20 infrared-transmitting between 3000 and 300 cm" ). It should be noted that the MIR technique yields good results only if used in clean, carefully controlled conditions. 

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