Spectral Overlaps

Allowance for spectral overlap, the effect of pressure, and the effect of soot luminosity would make computation tedious. Table 5-8 gives constants for use in direct calculation, for H9O/CO9 mixtures, of the product cT The product term is used because it varies much less with T than does c alone. Constants are given for mixtures, in nonradiat-ing gases, of water vapor alone, CO9 alone, and four p Jpc mixtures. 

Combined Soot W2O, and CO2 Radiation The spectral overlap of H9O and CO9 radiation has been taken into account by the constants for obtaining Ec- Additional overlap occurs when soot emissivity , is added. If the emission bands of water vapor and CO9 were randomly placed in the spectrum and soot radiation were gray, the combined emissivity would be Eg phis , minus an overlap correction g s- But monochromatic soot emissivity is higher the shorter the wavelength, and in a highly sooted flame at 1500 K half the soot emission hes below 2.5 [Lm where H9O and CO9 emission is negligible. Then the correction g s must be reduced, and the following is recommended ... 

VEELS spectra are limited in practice to tbe relatively narrow energy range of about 30 eV over wbicb plasmons or interband transitions can occur. In contrast to AES, XPS, or even CEELS, where excitations can occur over hundreds of eV, the probability of spectral overlap is much higher for VEELS. It is fortunate that most... 

REELS will continue to be an important surface analytical tool having special features, such as very high surface sensitivity over lateral distances of the order of a few pm and a lateral resolution that is uniquely immune from back scattered electron effects that degrade the lateral resolution of SAM, SEM and EDS. Its universal availability on all types of electron-excited Auger spectrometers is appealing. However in its high-intensity VEELS-form spectral overlap problems prevent widespread application of REELS. 

Detection limits for a particular sample depend on a number of parameters, including observation height in the plasma, applied power, gas flow rates, spectrometer resolution, integration time, the sample introduction system, and sample-induced background or spectral overlaps. ... 

Describes how spectrometer resolution affects detection limits in the presence and absence of spectral overlaps. 

Spectral interferences in AAS arise mainly from overlap between the frequencies of a selected resonance line with lines emitted by some other element this arises because in practice a chosen line has in fact a finite bandwidth . Since in fact the line width of an absorption line is about 0.005 nm, only a few cases of spectral overlap between the emitted lines of a hollow cathode lamp and the absorption lines of metal atoms in flames have been reported. Table 21.3 includes some typical examples of spectral interferences which have been observed.47-50 However, most of these data relate to relatively minor resonance lines and the only interferences which occur with preferred resonance lines are with copper where europium at a concentration of about 150mgL 1 would interfere, and mercury where concentrations of cobalt higher than 200 mg L 1 would cause interference. 

Self-assembly of functionalized carboxylate-core dendrons around Er +, Tb +, or Eu + ions leads to the formation of dendrimers [19]. Experiments carried out in toluene solution showed that UV excitation of the chromophoric groups contained in the branches caused the sensitized emission of the lanthanide ion, presumably by an energy transfer Forster mechanism. The much lower sensitization effect found for Eu + compared with Tb + was ascribed to a weaker spectral overlap, but it could be related to the fact that Eu + can quench the donor excited state by electron transfer [20]. 

Spectral overlap of emission and absorption wavelengths Is a potential cause of Interference In atomic absorption spectrometry (57) Thus, (a) the emission line of Fe at 352.424 nm Is close to the resonance line of N1 at 352.454, (b) the emission line of Sb at 217.023 nm Is close to the resonance line of Pb at 216.999 nm, and (c) the emission line of As at 228.812 nm Is close to the resonance line of Cd at 228.802 (57). To date, these practically coincident spectral lines have not been reported to be of practical Importance as sources of analytical Interference In atomic absorption analyses of biological materials. 

Norris, J. D. and West, T. S. "Some Applications of Spectral Overlap in Atomic Absorption Spectrometry . Anal. 

Similarly, some INAA data contributed to the derivation of a reference value for Ba in SDO-i were biased high by an interference from Ru (Wandless 1993). The Ru is a fission product of U, whose concentration of 40 qg/g is relatively high in SDO-1. In this case, no appropriate reference sample was available for analysis to control the SDO-1 results the interference was identified through the disagreement between INAA data and data produced using XRF and ICP-AES methods on the same sample. A bias-free method again resulted when analysis of an atypical type led to detection of a rarely encountered but sizeable spectral overlap. Once identified, correction was straightforward. 

International or in-house standards in combination with fundamental parameters software, lead to the same accuracy as conventional analysis using regression analysis of standards. Provided that accurate standards are available, the main factors that determine the accuracy of XRF are the matrix absorption correction and (in the case of EDXRF) the spectrum evaluation programme, i.e. correction for spectral overlap and background. 

Et /ZG AG -0.2 V fluorescence quenching correlates with CT driving force no spectral overlap for energy transfer no Zs in injection site or intervening sequence k = 2 x 1011 s 1 observed up to 20 A in time-resolved and steady-state experiments shallow dependence of CT yield between 6-24 A (y = 0.2-0.3) no dependence of kci between 10-17 A strong efficiency and distance dependence of CT yield vary with Z flanking sequence and intervening mismatches... 

It is possible to estimate the rate of vertical singlet energy transfer (9.31) and (9.33) (when Forster-type energy transfer is negligible, spectral overlap integral is very small) from the relation... 

Takakusa H, Kikuchi K, Urano Y, Kojima H, Nagano T (2003) A novel design method of ratiometric fluorescent probes based on fluorescence resonance energy transfer switching by spectral overlap integral. Chemistry 9 1479-1485... 

For the dilute aH spins surrounded by a large number of the 2H spins, the heteronuclear aH-H dipolar interaction is dominant, lifting the spectral overlap between the 1H packets. H spin diffusion is driven by the flip-flop term of the 1H-1H dipolar interaction, which becomes secular in the presence of spectral overlap. Thus, spin diffusion would be accelerated if it had not been for the 1H-2H dipolar interaction. In order to confirm this prediction, they used another RF channel of the OPENCORE... 

Figure 4. IR spectra in D -doped liquid Kr at -120°C of (OC) Cr(ol) and of the photolysis product (OC) Cr(ol)(D ) [ol = trans-cyclooctene]. D2 was used rather than H2 to avoid potential spectral overlap of any V(H-H) bands with bands due to the hydrocarbon ligand.

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