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Differential absorption obscuring

The three terms in equation 67 can be considered individually. The first term is the differential absorption flattening term, the second the differential absorption obscuring term and the third the differential light scattering term. [Pg.333]

The calculated value for equation 73 is plotted as curve b in Figure 42, where the shape of the ORD curve is seen to parallel it very closely. This component of differential light scattering does not include the effects of the mixed term, i.e., the absorption obscuring term. When this is included the value A[0] (curve c of Figure 42) is obtained [112]... [Pg.336]

In applying RAIRS to CO adsorption, the contribution from CO molecules in the gas phase to the absorption spectrum at CO pressures above 10-3 mbar completely obscures the weak absorption signal of surface adsorbed CO. Beitel et al. found it possible to subtract out the gas phase absorption by coding the surface absorption signal by means of the polarization modulation (PM) technique applied to a conventional RAIRS spectrometer, p-polarised light produces a net surface electric field which can interact with adsorbed molecules, whereas both polarization states are equally sensitive to gas phase absorption because gas phase molecules are randomly oriented. By electronic filtering a differential spectrum is computed which does not show contributions from the gas phase and which has much higher surface sensitivity than a conventional RAIRS setup. [Pg.45]

Adsorbed moleeules and intermediates at high pressures can be detected by vibrational speetroseopies provided they can differentiate between gas phase and surfaee signals. For example, Fig. 4 shows a (conventional) IRAS spectrum of CO at 50mbar on Pd(l 11) at 300 K (113,114). The signal of adsorbed on-top CO at approximately 2060 cm is nearly obscured by the rovibrational absorption spee-trum of the CO gas phase. In contrast, as shown below, SFG and PM-IRAS selectively probe the adsorbed surface species and thus provide surface-sensitive information, even in the presence of a gas phase. Investigations of the catalyst structure and composition under working conditions can be earried out by high-pressure (HP-) STM and (HP-) XPS, provided that the instruments are properly modified (9,115). [Pg.143]

At the same time, we want to focus on the role of diffusion in extraction, for that is the subject of this book. As a result, we emphasize the case of a dilute solute being extracted between two immiscible liquids. This defers complicated issues of ternary phase equilibria to more specialized texts and lets us focus on the issues of mass transfer, which can be obscured in those texts. Specifically, we discuss extraction equipment in Section 14.2, we analyze differential extractors as a parallel to gas absorption in Section 14.3, and we describe staged extraction in Section 14.4. Leaching, which can be either staged or differential, is treated in Section 14.5. The result is a brief summary that emphasizes the role of mass transfer. [Pg.404]


See other pages where Differential absorption obscuring is mentioned: [Pg.333]    [Pg.333]    [Pg.333]    [Pg.333]    [Pg.77]    [Pg.339]    [Pg.140]    [Pg.29]    [Pg.591]    [Pg.21]   
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