Spectroscopy Fourier-transform

described in the previous section has been used very successfully for high-resolution spectroscopy in the infrared region. The basic idea, already discussed above, is the transfer of the high frequencies oj of the incident radiation to audio frequencies Aw = 2(v/c)o) of the interference pattern by the uniform motion of mirror M2 with constant velocity v. 

Assume that the incoming radiation is composed of several components with frequencies wj. The total amplitude in the plane B of the detector is the sum of all interference amplitudes (4.39), 

A detector with a time constant large compared with the maximum period l/o3 does not follow the rapid oscillations of the amplitude at frequencies 03 or at the difference frequencies but gives a signal proportional 

When the incoming wave consists of two components with frequencies 03 and 0)2, the interference pattern will vary with time according to 

Interference signal from an incoming wave with two components wi and 

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Ernst R R and Anderson W A 1986 Application of Fourier transform spectroscopy to magnetic resonance Rev. Sc/. Instrum. 37 93-102... 

Fourier transform spectroscopy in the radio frequency region has been applied most importantly in pulsed Fourier transform NMR spectroscopy, which is not a subject which... 

Diffuse reflectance infrared Fourier transform spectroscopy... 

Beer, R., "Remote Sensing by Fourier Transform Spectroscopy." Wiley, New York, 1992. Cracknell, A. P., "Introduction to Remote Sensing." Taylor Francis, New York, 1991. Keith, L. H., "Environmental Sampling and Analysis." Lewis Publishers, Chelsea, MI, 1991. 

Griffitbs, RR., Chemical Infrared Fourier Transform Spectroscopy. John Wiley and Sons, New York, NY, 1975. 

Spectra of a mixture of 240,242,244pu js0t0pes recorded by Fourier-transform spectroscopy. 

It is the self-coherence function that is measured in Fourier transform spectroscopy. Writing the measured on-axis intensity at the output of the Michelson interferometer as... 

Time-resolved Fourier transform infrared spectroscopy has been used surprisingly little considering the nuadter of commercial spectrometers that are currently in laboratories and the applicability of this technique to the difficult tine regime from a few is to a few hundred is. One problem with time-resolved Fourier transform spectroscopy and possibly one reason that it has not been more widely used is the stringent reproducibility requirement of the repetitive event in order to avoid artifacts in the spectra( ). When changes occur in the eiaissirr source over the course of a... 

From Table 2 it is observed that the dispersive NIR ensembles (NIR and NIR R) result in the best cross validated models. The potential advantages of Fourier transform spectroscopy [5] are in practice outnumbered by a more reproducible setup and saimpling procedures. 

Fourier-transform spectroscopy ELP-DAD Extended light path diode-array... 

Diffuse Reflectance IR Fourier Transform Spectroscopy (DRIFTS) can be employed with high surface area catalytic samples that are not sufficiently transparent to be studied in transmission. In this technique, the diffusely scattered IR radiation from a sample is collected, refocussed, and analysed. Samples can be measured in the form of loose powders. 

Diffuse reflectance infrared Fourier transform spectroscopy deuterium triglycine sulphate energy compensated atom probe energy dispersive analysis energy-loss near edge structure electron probe X-ray microanalysis elastic recoil detection analysis (see also FreS) electron spectroscopy for chemical analysis extended energy-loss fine structure field emission gun focused ion beam field ion microscope... 

It is instructive to consider a specific example of the method outline above. The triangle fimction (l/l) a (x/l) was discussed in Section 11.1.2. It was pointed out there that it arises in dispersive spectroscopy as the slit function for a monochromator, while in Fourier-transform spectroscopy it is often used as an apodizing function. Its Fourier transform is the function sine2, as shown in Fig. (11-2). The eight points employed to construct the normalized triangle fimction define the matrix... 

Although acetone was a major product, it was not observed by infrared spectroscopy. Flowing helium/acetone over the catalyst at room temperature gave a prominent carbonyl band at 1723 cm 1 (not show here). In this study, a DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy) cell was placed in front of a fixed reactor DRIFTS only monitored the adsorbed and gaseous species in the front end of the catalyst bed. The absence of acetone s carbonyl IR band in Figure 3 and its presence in the reactor effluent suggest the following possibilities (i) acetone formation from partial oxidation is slower than epoxidation to form PO and/or (ii) acetone is produced from a secondary reaction of PO. 

The experimental system consists of three sections (i) a gas metering section with interconnected 4-port and 6-port valves, (ii) a reactor section including an in-situ diffused reflectance infrared Fourier transform spectroscopy reactor (DRIFTS) connected to tubular quartz reactor, (iii) an effluent gas analysis section including a mass spectrometer or a gas chromatograph (9). 

In this contribution, the steady-state isotopic transient kinetic analysis-diffuse reflectance Fourier transform spectroscopy (SSITKA-DRIFTS) method provides further support to the conclusion that not only are infrared active formates likely intermediates in the water-gas shift (WGS) reaction, in agreement with the mechanism proposed by Shido and Iwasawa for Rh/ceria, but designing catalysts based on formate C-H bond weakening can lead to significantly higher... 

Fig. 2. PTI spectrum of a p-type, ultra-pure Ge sample, obtained by Fourier transform spectroscopy. The sample contains the acceptors B, Al, and A(D,C) in a total concentrations of 6 x 1010 cm-3. The most narrow lines are 0.09 cm-1 ( = 11 peV) wide. 

Bell, R.J. (1972). Introductory Fourier Transform Spectroscopy. Academic Press, New York. Blakemore, J.S. (1987). Semiconductor Statistics. Dover Publ. Inc., New York. 

From a practical point of view, the optical detection of possible X—H bonds in hydrogenated samples is performed at LHeT as a better sensitivity is obtained at this temperature because the features are sharper than the ones observed at ambient. The sensitivity of Fourier Transform Spectroscopy (FTS) allows usually a normal incidence geometry of the optical beam. Two kinds of samples are generally used in the hydrogenation studies. The first are thin epitaxial layers (1 to 5 in thickness) with dopant concentrations in the 1017-102° at/cm3 range on a semi-insulating... 

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 ... 

Diffuser aerators, jet air, 26 165 Diffuse reflectance, 14 231 Diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), 24 72, 110-111... 

DRIFT spectra, acquiring, 24 111. See also Diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) Drilling, of hydrothermal wells, 12 525-527 Drilling fluid (drilling mud) companies, 9 2 Drilling fluid materials, 9 2, 9-25. See also Drilling fluids Drilling muds alkalinity control in, 9 19 barite, 9 9-10 calcite, 9 10... 

Fourier transform spectroscopy diffuse reflectance infrared, 24 72, 110-111... 

Direct NIR or MIR measurements of whole soil can be made using attenuated total reflectance (ATR) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) samplers. This type of measurement detects only components on the surface and so has severe limitations when information about the bulk soil is needed [4],... 

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