Fourier-transform reflection absorption

Matsuda, Y., Akazawa, R.,Teraoka, R., and Totsuka, M. (1994), Pharmaceutical evaluation of carbamazepine modifications Comparative study of photostability of carbamazepine polymorphs by using fourier-transformed reflection-absorption infrared spectrocopy and colorimetric measurement, / Pharm. Pharmacol., 46,162-167. 

Matsuda Y, Akazawa R, Teraoka R, Otsuka M. Pharmaceutical analysis of carbamazepine modifications comparative study of the photostability of caba-mazepine polymorphs by Fourier-transformed reflection-absorption infrared spectroscopy and colorimetric measurements. J Pharm Pharmacol 1994 46 162-167. 

Teraoka R, Otsuka M, Matsuda Y. Evaluation of photostability of solid state dimethyl l,4-dihydro-2,6-dimethyl-4-(2-nitro-phenyl)-3,5-pyridinecarboxylate by Fourier-transformed reflection-absorption infrared spectroscopy. Int J Pharm 1999 184 35-43. 

Nondestructive Evaluation of Aging in Cotton Textiles by Fourier Transform Reflection—Absorption Infrared Spectroscopy... 

Hayden, B.E., King, A. and Newton, M.A. (1999) Fourier transform reflection absorption IR spectroscopy study of formate adsorption on TiO2(110). 

Attention in this chapter will be mainly focused on che reaction of tecrahydrofuran (THF) with thin lithium films vapor-deposited in UHV on clean polycrystalline Ag substrates. The techniques employed in this study included TPD, XPS and AES. A parallel study of THF adsorption on Li layers deposited on Au substrates is currently being pursued by Ms. Guorong Zhuang using FTIRRAS (Fourier Transform Reflection Absorption Infrared Spectroscopy) in this laboratory. 

FT RAIRS (Fourier transform reflection-absorption infrared spectroscopy)... 

Fourier transform reflection-absorption infrared (RA-IR) spectroscopy is used to probe the structure and properties of sodium dodecyl sulfonate (C12S) monolayers that are self-assembled from dilute solution at an air-water interface. Recent optical models for the interpretation of signal intensity measurements are briefly reviewed. The methylene stretching peaks of C12S monolayers in the RA-IR spectra are used to determine die chain orientation, the surface concmtration and the conformational state of the alkyl chains. Conqiarisons are drawn between monolayers and C12S crystals. A phase transition is found as the concentration of C12S in the subphase below the monolayer is reduced. The effect of salt on the monolayers is presented. The infrared data is interpreted in terms of the surface tension behavior. 

Also, Fourier transform infrared absorption spectroscopy provides relevant information regarding the specific interactions of different probes within substrates [17], especially in the diffuse-reflectance mode when applied to the study of powdered opaque surfaces that disperse the incident radiation. The extension of this technique to obtain time resolved transient absorption spectra in the IR wavelength range (laser flash-photolysis with IR detection) will certainly play in the near future an important role in terms of clarifying different reaction mechanisms in the surface photochemistry field [17c, 18]. 

It is interesting to note that a similar specttum of the 0-0 band of the a-X system, leading to the same value of the absorption intensity, has been obtained using a Fourier transform spectrometer (see Section 3.3.3.2) but with an absorption path, using a multiple reflection cell, of 129 m and half the pressure of gas. 

Recent work in our laboratory has shown that Fourier Transform Infrared Reflection Absorption Spectroscopy (FT-IRRAS) can be used routinely to measure vibrational spectra of a monolayer on a low area metal surface. To achieve sensitivity and resolution, a pseudo-double beam, polarization modulation technique was integrated into the FT-IR experiment. We have shown applicability of FT-IRRAS to spectral measurements of surface adsorbates in the presence of a surrounding infrared absorbing gas or liquid as well as measurements in the UHV. We now show progress toward situ measurement of thermal and hydration induced conformational changes of adsorbate structure. The design of the cell and some preliminary measurements will be discussed. 

Reaction products can also be identified by in situ infrared reflectance spectroscopy (Fourier transform infrared reflectance spectroscopy, FTIRS) used as single potential alteration infrared reflectance spectroscopy (SPAIRS). This method is suitable not only for obtaining information on adsorbed products (see below), but also for observing infrared (IR) absorption bands due to the products immediately after their formation in the vicinity of the electrode surface. It is thus easy to follow the production of CO2 versus the oxidation potential and to compare the behavior of different electrocatalysts. 

Different experimental approaches were applied in the past [6, 45] and in recent years [23, 46] to study the nature of the organic residue. But the results or their interpretation have been contradictory. Even at present, the application of modem analytical techniques and optimized electrochemical instruments have led to different results and all three particles given above, namely HCO, COH and CO, have been recently discussed as possible methanol intermediates [14,15,23,46,47]. We shall present here the results of recent investigations on the electrochemical oxidation of methanol by application of electrochemical thermal desorption mass spectroscopy (ECTDMS) on-line mass spectroscopy, and Fourier Transform IR-reflection-absorption spectroscopy (SNIFTIRS). 

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. 

In the diffuse reflectance mode, samples can be measured as loose powders, with the advantages that not only is the tedious preparation of wafers unnecessary but also diffusion limitations associated with tightly pressed samples are avoided. Diffuse reflectance is also the indicated technique for strongly scattering or absorbing particles. The often-used acronyms DRIFT or DRIFTS stand for diffuse reflectance infrared Fourier transform spectroscopy. The diffusely scattered radiation is collected by an ellipsoidal mirror and focussed on the detector. The infrared absorption spectrum is described the Kubelka-Munk function ... 

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