Spectral overlap, absorption spectroscopy

Typical examples of n >n UV spectra are illustrated in Tables XIII-XVI. The use of absorption spectroscopy for diagnostic purposes is limited. Thus simple 2//-pyrans, as a rule, show more complex and red-shifted absorption curves in comparison to those of similar 4//-pyrans (Tables XIII and XIV). Analogous spectral behavior for simple 2H- and 4H-thiopyrans is perceptible from Tables XV and XVI. The introduction of conjugating aryl groups and other unsaturated substituents causes a significant overlap of original absorption bands with those of the aromatic systems as well as a bathochromic shift of the longest wave absorption maxima. 

The high molecular specificity of Raman spectra results in less spectral overlap than other modalities such as NIR absorption spectroscopy, thus enabling the detection of low signal strength components such as glucose. 

This increased spectral information can be maximised still further by applying the same chemometric principles used in NIR. If a derivative is apphed to the data, we can resolve overlapping absorptions to differentiate between components with essentially similar UV spectra. This does not however address fundamental issues with probe design. UV spectroscopy, like NIR uses transmission probes... 

Two types of interference are encountered in atomic absorption spectroscopy Spectral interference is a result of the absorption of an interfering species that either completely overlaps with the signal of interest or lies so close to this signal that it cannot be resolved by the monochromator. Chemical interference may be a consequence of the various chemical processes that occur during atomisation and alter the absorption characteristics of the analyte. 

Tune-resolved measurements are widely used in fluorescence spectroscopy, particularly for studies of biological macromolecules. This is because time-iesolved data fie-quently contain more information than is available frcnn the steady-state data. For instance, consider a protein which contains two tryptophan residues, each with a distinct 11 fetime. Because of spectral overlap of the absorption and emission, it is not usually possible to resolve the onission from the two residues. However, the tune-resolved data may reveal two decay times, which can beused to resolve the emission spectra and relative intensities of the two tryptophan residues. Then one can question how each of the tryptophan residues is affected by the interactions of the protein with its substrate or other macromolecules. Is one of the tryptophan residues close to the binding site Is a tryptophan residue in a distal domain affected by substrate binding to another domain Such questions can be answered if one measures the decay times associated with each tryptophan residue. 

With these favorable circumstances, the HREEL spectrum of poiyimide reveals a large number of vibrational bands, quite well resolved from each other. In order to help band assignments, IR transmission spectrum, or Fourier Transform IRAS (Infrared Reflection Absorption Spectroscopy) spectra, from model ODA, PMDA and PMDA-ODA surfaces can be used. These last spectral data have been superimposed on the HREEL spectrum, in the 1000-2(XX) cm i region, where a number of vibrational bands do signiflcandy overlap (Fig. 2). It is quite clear that all the different chemical sites have their fingerprints t... 

The rate and relative amplitude of slow injection from the triplet state differ from report to report. Since some groups use only visible/NIR transient absorption spectroscopy, the oxidized Ru-complex, which appears at around 800 nm, cannot be spectrally distinguished very well from the overlapping... 

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