DRIFT spectroscopy Subject

Diffuse reflectance IR spectroscopy has become an attractive alternative to mulls with the introduction of DRIFT cell by Griffiths,29 later modified by Yang.30 Since materials are dispersed in a nonabsorbing medium and not subjected to thermal or mechanical energy during sample preparation, DRIFT spectroscopy is especially suitable for the qualitative/quantitative analysis for polymorphs, which are prone to solid-state transformations. The Kubelka-Munk (K-M) equation,31 which is analogous to Beer s law for transmission measurements, is used to quantitatively describe diffusely-reflected radiation ... 

The details in the CO response continue to be the subject of many discussions and a full explanation will need further studies. These can include spectroscopy studies such as diffuse reflectance transform infrared spectroscopy (DRIFT), which can be performed under realistic conditions [43,44], and theoretical modeling [45]. However it seems likely that not only hydrogen gives rise to charged or polarized complexes on the insulator surface. Equation (2.3) may now be written as... 

The constitution of oxygen-containing sites in carbonaceous materials of various types was a subject of inquiry of many authors. The first systematized results were outlined in a review by Boehm [77]. In the past few years numerous researches were carried out applying the diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) technique [78-81], and their results were summarized in a paper by Fanning and Vannice [82]. Analogous results concerning... 

The metal supported catalysts were characterized by FTIR spectroscopy, TEM analyses, surface area and metal dispersion determinations. The 5% Ru/Nb205 catalysts, discharged after the activity tests, were subjected to pulse NO chemisorption in a ZnSe DRIFTS cell at 423 and 523 K. 

FIGURE 9.4 Use of the reference point for taking into account the image drift (a) position of the reference point on an area of 2000 x 2000 nm (shown with an arrow) (b) the same area repeatedly recorded 15 min later (the area subjected to spectroscopy is denoted with the square, its upper left comer coincides with the reference point). 

With a warning to the students, we have selected electron volts as the most useful energy unit to relate spectroscopy experiments to theory in the sense that a student can imagine the physical units. However, the physical constants are revaluated every three years or so which makes past research papers subject to drift in the values of the constants. Around 1960, quantum chemists addressed this problem and chose yet another set of units in which c = h = m = q = lto simplify theoretical equations in atomic units, so that the equations were expressed totally in the basic mathematical units. In these units (used by quantum chemistry computer programs), a person only needs to know the latest value of an energy unit called the hartree and the latest value of the Bohr radius (ao) to convert computer results back to laboratory results. At present (2010), 1 hartree = 27.2113845 eV... 

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