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. 

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]... 

However, application of the above technique can be problematic when strong solution-phase absorption obscures weak bands of a surface species. To overcome this limitation, the phase rotation approach [263] can be used. Phase-sensitive detection such as with a lock-in amplifier (LIA) provides two signals the signal that is in phase IP) and the signal that is out of phase (the quadrature, Q) with the external perturbation [264]. These quantities can be represented at each... 

The effect of a basic solvent upon the low-frequency modes is discernible in only the highest frequency mode, because solvent absorption obscures the lower frequency region. The 550-500 cm band is shifted to lower... 

The UV spectra of quinoxalines have been examined in several solvents. In cyclohexane, three principal absorptions are observed (Table 2). In hydroxylic solvents the vibrational fine structure disappears and in methanol or water the weak n- ir transitions are obscured by the intense ir->ir transition (79HC(35)l). 

Z values are obtained from Eq. (8-76) for solvents having Z in the approximate range 63-86. In more polar solvents the CT band is obscured by the pyridinium ion ring absorption, and in nonpolar solvents l-ethyl-4-carbomethoxy-pyridinium iodide is insoluble. By using the more soluble pyridine-1-oxide as a secondary standard and obtaining an empirical equation between Z and the transition energy for pyridine-1-oxide, it is possible to measure the Z values of nonpolar solvents. The value for water must be estimated indirectly from correlations with other quantities. Table 8-15 gives Z values for numerous solvents. 

Polymeric Sn is dark yellow with an absorption edge at 350 nm (cf. p. 683) but the colour is often obscured either by the presence of trace organic impurities or, in pure S, by the presence of other highly coloured species such as the dark cherry-red trimer S3 or the deeper-colouied diradicals S4 and S5. 

The intense blue color which is obtained when tryptophan, in the presence of an aldehyde, is treated with concentrated sulfuric acid containing an oxidizing agent (Adamkiewicz-Hopkins-Cole reaction) was beheved to involve formation of a tetrahydro-j8-carboline intermediate, since most l,2,3,4-tetrahydro-j8-carbohne derivatives yield a similar color with concentrated sulfuric acid containing an oxidizing agent. The two colors have now been shown to have different absorption spectra. The nature of the carboline-blue color is still obscure. 

The Raman spectrum of an oxide sample after adsorption may be considered to consist of the spectrum of the adsorbed species superimposed on the spectrum due to the oxide adsorbent. In general, the Raman spectra of oxide adsorbents are sufficiently weak or sufficiently simple that they allow the detection of Raman lines due to the adsorbed species. This is one major advantage of Raman scattering over infrared absorption spectroscopy. The infrared spectra of most oxide adsorbents show strong absorptions which may obscure those arising from the adsorbates (Figs. 13,14). 

Smoke detection depending upon absorption of ionizing radiation by smoke particles light scattering by smoke particles light obscuration. 

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