Efficiency factor Extinction Scattering

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

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. 

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 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... 

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 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... 

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... 

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... 

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. 

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... 

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