Fast Fourier transform infrared spectroscopy

Fast Fourier Transformed Infrared Spectroscopy (FTIR)... 

Other combinations of chromatography techniques with MS which may be useful in environmental studies are the coupling of high performance liquid chromatography (LC) with MS [84,384,504,506,530,585-593],LC with MS-MS [181, 594 - 599], LC with atmospheric pressure chemical ionization MS (LC-APCI-MS) [600], and Fourier transform infrared spectroscopy-fast atom bombardment coupled to LC-MS (FTIR-FAB-LC-MS) [514]. 

Infrared and Raman spectroscopy, coupled with optical microscopy, provide vibrational data that allow us to chemically characterise geochemical sediments and weathered samples with lateral resolutions of 10-20 pm and 1-2 pm respectively. Fourier transform infrared spectroscopy involves the absorption of IR radiation, where the intensity of the beam is measured before and after it enters the sample as a function of the light frequency. Fourier transform infrared is very sensitive, fast and provides good resolution, very small samples can be analysed and information on molecular structure can be obtained. Weak signals can be measured with high precision from, for example, samples that are poor reflectors or transmitters or have low concentrations of active species, which is often the case for geochemical sediments and weathered materials. Samples of unknown... 

FAST THERMOLYSIS-FOURIER TRANSFORM INFRARED SPECTROSCOPY METHODS TO STUDY ENERGETIC MATERIALS... 

Toward filling these voids, we have developed several fast thermolysis/Fourier transform infrared spectroscopy techniques that permit near real-time studies of energetic materials heated at 70-400 C/sec under selected pressures in the 1-1000 psi range. These techniques are described in the companion article for this Institute. 

Fast Fourier Transformation is widely used in many fields of science, among them chemoractrics. The Fast Fourier Transformation (FFT) algorithm transforms the data from the "wavelength" domain into the "frequency" domain. The method is almost compulsorily used in spectral analysis, e, g., when near-infrared spectroscopy data arc employed as independent variables. Next, the spectral model is built between the responses and the Fourier coefficients of the transformation, which substitute the original Y-matrix. 

As mentioned, we also carried out IR studies (a fast vibrational spectroscopy) early in our work on carbocations. In our studies of the norbornyl cation we obtained Raman spectra as well, although at the time it was not possible to theoretically calculate the spectra. Comparison with model compounds (the 2-norbornyl system and nortri-cyclane, respectively) indicated the symmetrical, bridged nature of the ion. In recent years, Sunko and Schleyer were able, using the since-developed Fourier transform-infrared (FT-IR) method, to obtain the spectrum of the norbornyl cation and to compare it with the theoretically calculated one. Again, it was rewarding that their data were in excellent accord with our earlier work. 

An important tool for the fast characterization of intermediates and products in solution-phase synthesis are vibrational spectroscopic techniques such as Fourier transform infrared (FTIR) or Raman spectroscopy. These concepts have also been successfully applied to solid-phase organic chemistry. A single bead often suffices to acquire vibrational spectra that allow for qualitative and quantitative analysis of reaction products,3 reaction kinetics,4 or for decoding combinatorial libraries.5... 

Since the article by Spedding1 on infrared spectroscopy and carbohydrate chemistry was published in this Series in 1964, important advances in both infrared and Raman spectroscopy have been achieved. The discovery2 of the fast Fourier transform (f.F.t.) algorithm in 1965 revitalized the field of infrared spectroscopy. The use of the f.F.t., and the introduction of efficient minicomputers, permitted the development of a new generation of infrared instruments called Fourier-transform infrared (F.t.-i.r.) spectrophotometers. The development of F.t.-i.r. spectroscopy resulted in the setting up of the software necessary to undertake signal averaging, and perform the mathematical manipulation of the spectral data in order to extract the maximum of information from the spectra.3... 

In Fourier transform infrared (FTIR) spectroscopy, simply one beam is used during the IR analysis of a sample, that is, in this case, all frequencies go through the instrument at one time [61] (see Figure 4.18). The method is called FTIR spectroscopy, because a Fourier transformation is carried out by a computer in order to work out the obtained data and yield a spectrum. FTIR is fast, that is, a spectrum can be obtained in less than a second. Besides, it is a very sensitive technique, because it is possible to make as many scans as necessary to obtain a good spectrum. 

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