Fluorescence effects

Fluorescence effects are, in general, considered to be negligible. In gas-filled detectors the corresponding photons are discarded in the energy discrimination stage of... 

Unfortunately, the fluorescent effect is not directly proportional to the concentration of colorant present, since there is considerable quenching if quite low concentrations are exceeded. The light fastness of the fluorescent pigments is also less than that of many other organic pigments now available, but improvement can be achieved using overlayers containing ultra-violet absorbers. This is an area in which further research will clearly be needed. 

Fluorescence spectroscopy is commonly used to characterize fluorescence effects in the UV and visual range of the electromagnetic spectrum. Such fluorescence is caused by the fact that the absorption of UV or visible light of specific wavelengths causes excitation of electrons within a molecule. If radiating relaxation occurs directly from the singlet Sj state, the process is called fluorescence. 

Novel helical polybinaphthyls, including 38, have been synthesized, and their structures were characterized by NMR, UV, FL, and CD. Their optical properties have also been studied, and it was observed that these compounds exhibit a significantly increased fluorescence effect to an amino alcohol quencher over the parent l,l -bi-2-naphthol < 2004MM 2695 >. 

AFI has an additional advantage over the Raman approach since the peripheral reference location allows one to eliminate, in first order, any potentially confounding attenuation effects arising from anterior optical media. Also, AFI-derived MP results can be obtained with one image only. On the other hand, this method is not as specific, however, compared to Raman, and care has to be taken to avoid potentially confounding fluorescence effects from anterior ocular media such as the lens. 

Messerschmidt and Chase (41) recently demonstrated that it was feasible to use a microscope to obtain the FT-Raman effect. Transfer of laser energy occurs through collection optics in their instrument. Figure 3-11 illustrates the spectrum of a single strand (12/nn in diameter) of Kevlar polymer as accomplished by FT-Raman microscopy. Kevlar is difficult to measure by conventional Raman spectroscopy because of fluorescence effects. 

In EDX experiments on thick samples, for example in SEM, almost all the energy of the incident electron beam is consumed to produce X-rays and the number of atoms in a sample can be calculated from the X-ray intensities in the EDX spectra, by carrying out the ZAF calibration (Z = the atomic number effect A = the absorption effect and F = the fluorescence effect) [18]. However, HRTEM specimens are usually thin, 200nm or less. In this case, most electrons in the incident beam will pass through the specimen and the ZAF calibration cannot be done. In practice, we use some standard specimens (whose compositions are known) as references to obtain a relative composition of a target sample. 

Low sling, low viscosity fluorescent coning oil. Imparts a super-white fluorescent effect on nylon. 

Yamaguchi, T., Kaya, T., and Takei, H. (2007). Characterization of capshaped silver particles for surface-enhanced fluorescence effects. Analytical Biochemistry hM 171-179. 

Finally, the fluorescent effect that expresses the possibility for an X-ray emitted in the sample to, in turn, excite an atom of the matrix (generally with an atomic number Z - I orZ-2). 

UV, fluorescence effect of H bonding, [Pg.423]

N. Mataga and S. Tsuno. Natur-wissenschaften 44, 304-5 (1957) (in English). UV, fluorescence effect of H bonding, acridine in CHCls, C2H5OH, CUCCOOH, etc. 

If moderately strong x-rays emanated from the bones and teeth of this body or if radiation came from surrounding rocks or soil, then some of the x-rays would have been absorbed by elements at the surface of the body, such as sodium, silicon, phosphorus, sulfur, chlorine, potassium, and calcium, as well as carbon, oxygen, and nitrogen, and characteristic x-rays of relatively long wavelengths would be emitted due to an x-ray fluorescence effect. 

Use Red dye for paper, also for wool and silk where brilliant fluorescent effects are desired and light-fastness is of secondary importance analytical reagent for certain heavy metals, biological stain. 

The fluorescence factor (F) arises from the excitation of characteristic X-rays of the element to be analyzed by the characteristic X-rays emitted from matrix atoms. This phenomenon occurs when the characteristic X-rays from matrix elements have energies greater than that required for exciting characteristic X-rays of the element to be analyzed. Thus, the resulting X-ray intensities of the element to be analyzed will be enhanced by the fluorescence effect. The fluorescence factor is usually least important in the matrix factor, because fluorescence X-rays may not exist, or the concentration of elements emitting fluorescence X-rays may be small. 

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