Extinction efficiency factor

Considering an incident plane wave on a sphere of no net surface charge, the scattering and extinction efficiency factor for the field far away from the particle can be approximated by [Van de Hulst, 1957]... 

Knowing R, the extinction efficiency factor (Q) can be found, by Mie scattering theory for the sphere [7], Then the particles concentration is N = y I (QnR2Lt2), where L is the distance between windows, t is the transparency of the window. 

The extinction efficiency factor Q , approaches a constant asymptotic value of 2 with increasing size parameter. It means that a large particle attenuates (absorbs and scatters) twice as much energy from an incident beam as characterized by its own geometric area. The additional attenuation is because of diffraction of the EM waves by the particle. This phenomenon... 

Brewster and Kunitomo [231] attempted to obtain coal refractive indices with a different approach. Following an earlier work by Janzen [226], they suspended coal particles in a KBr matrix and measured spectral transmission from the samples. Assuming particles are spherical and knowing the size distribution and volume fraction of coal in the sample, they predicted the extinction efficiency factor Qt . Using a dispersion equation curve fitting for Qe , they determined the complex index of refraction of different coal samples. They reported values for the absorption index kK that was an order of magnitude smaller than earlier studies. 

The extinction efficiency factor which is the sum of scattering efficiency factor Qsca and the absorption efficiency factor Qahs, is defined as the quotient of C xt and the physical cross-section area ttR. The scattering and absorption efficiency factors can be calculated according to the general Mie theory, which is explained, in some detail, below. Both can be expressed as infinite series (9). 

Cext is the extinction cross-section of the spheres. The extinction efficiency factor which is the sum of scattering and absorption, is defined as the quotient of and the... 

We may define efficiencies (or efficiency factors) for extinction, scattering, and absorption ... 

Qe Efficiency factor for extinction t/pt Particle terminal velocity... 

Rayleigh scattering for.v < 1 and the large particle extinction law for.v 1 provide useful limiting relationships for the efficiency factor. Frequently the range x 1 is imponani. 

The volumetric absorption, scattering, and extinction coefficients of polydispersions are related to efficiency factors as... 

Q Efficiency factors for particle absorption, extinction, scattering (m2), Eq. 7.180 q Radiative flux (W/m2)... 

The attenuation of light by a particle includes contributions from elastic scattering and absorption. The absorbed photons induce transitions leading to Raman or fluorescence scattering or contribute to the internal heating of the particle. The extinction cross section is the sum of the elastic-scattering cross section and the absorption cross section. The corresponding efficiency factors formed by... 

The extinction efficiency Qe), absorption efficiency (go) and anisotropy factor (g) for a cell embedded in an absorptive medium (the same as in Figure 7) are listed in Table 2. 

Fig. 3.8.3 Efficiency factors for extinction, Q, and absorption, Qa, for weakly absorbing particles.

Essentially, Cgcat and Cabs represent the electromagnetic powers removed from the incident wave as a result of scattering and absorption of the incident radiation, while Cext gives the total electromagnetic power removed from the incident wave by the combined effect of scattering and absorption. The optical cross-sections have the dimension of area and depend on the direction and polarization state of the incident wave as well on the size, optical properties and orientation of the particle. The efficiencies (or efficiency factors) for extinction, scattering and absorption are defined as... 

For the case of the foam board made up of only randomly oriented plateau borders, the weighted border extinction coefficient would be calculated under an assumption of a spherical border [9]. Specifically, the Mie Theory was utilized to quantify the efficiency factors for extinction and scattering of each single plateau border. The results were then extended to the entire foam morphology. For the foam board made up of only randomly oriented cell walls, the weighted wall extinction coefficient would be acquired once the intensities of... 

One factor which should be noted for palladium, which also applies to the observation of the transition metals Is that not all crystallites have the same efficiency for diffracting electrons, l.e., as the atomic number decreases, the extinction distance for the crystallite Increases (13). Thus one would anticipate Chat as the mean atomic number decreases, the crystallites will have Co be progressively larger to enable visual observation on a support such as alumina. 

For a typical monomolecular coverage, T — 10 10 mol/cm2, an electrode roughness factor r = 1000 and an extinction coefficient ads = 107 cm2/mol, the light-harvesting efficiency is, in comparison to the preceding case, very high, intimate contact with the semiconductor surface, hence the conditions for charge injection from S into the semiconductor are almost ideal (q9j—>100 per cent). 

The amount of fluorescence emitted by a fluorophore is determined by the efficiencies of absorption and emission of photons, processes that are described by the extinction coefficient and the quantum yield. The extinction coefficient (e/M-1 cm-1) is a measure of the probability for a fluorophore to absorb light. It is unique for every molecule under certain environmental conditions, and depends, among other factors, on the molecule cross section. In general, the bigger the 7c-system of the fluorophore, the greater is the probability that the photon hitting the fluorophore is absorbed. Common extinction coefficient values of fluorophores range from 25,000 to 200,000 M 1 cm-1 [4],... 

In choosing a fluorescent tag, the most important factors to consider are good adsorption (high extinction coefficient), stable excitation without photobleaching, and efficient, high quantum yield of fluorescence. Some fluorophores, such as fluorescein, exhibit rapid fluorescent quenching which lowers the quantum yield over time. Up to 50 percent of the fluorescent intensity observed on a fluorescein-stained slide can be lost within 1 month in storage. AMCA and... 

Plots of each of these quantities as a function of particle size would look quite different and, therefore, would tell different stories. Except for a scale factor, each of them plotted as a function of wavelength for the same particle size would be identical. In our first example of extinction (Fig. 4.6) we displayed the efficiency Qext, as we shall often do in this chapter. In Chapter 12, however, our preference switches to the extinction cross section per unit particle volume. Unnormalized extinction cross sections (strictly speaking, the differential scattering cross section integrated over the acceptance angle of the detector) are more appropriate in Section 13.5 on particle sizing. 

The light harvesting efficiency, or absorption factor, is related to the dye molar extinction coefficient ( ( ), L/mol/cm) and to the surface coverage ( , mol/cm2)... 

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