Extinction efficiency factor for

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

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

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... 

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]... 

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

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. 

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. 

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. 

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],... 

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 size of the signal depends on a number of factors in addition to the sensitivity of the bound-dye spectra to membrane potential. A light-dependent toxicity, termed photodynamic damage, has been documented and tabulated in the axon (3) and can severely limit the usefulness of a dye. The efficiency with which a dye penetrates through the glial cells encasing the axon and then binds to the excitable membrane is clearly critical. The extinction coefficient and, for fluorescence, the emission quantum yield are... 

Because of the scattering in the visible portion of the spectrum, any extinction due to colloidal Pb would be masked and consequently it has not been possible to date to observe the tpyical colloidal extinction due to irradiation as observed in single crystals [7, 8, 59]. However, Garrett [85] has found that the quantum efficiency for N2 evolution from single crystals is within a factor of approximately two of that reported by Hall and Williams [96] for films for 330 nm irradiation. While the wavelength dependence of the quantum efficiencies for... 

---