Extinction Absorption Scattering

I f multiple scattering is negligible the irradiance of a beam of light is exponentially attenuated from /, to It in traversing a distance h through a particulate medium (see Section 3.4)  

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Figure 10.7 Calculated spectra of extinction, absorption, and scattering efficiencies for different sized Au nanoparticles (a) d = 20 nm, (b) d = 40 nm, (c) d= 80 nm. (d) Nonresonant (polystyrene) particles, d = 300 nm.128 Qext, Qats, and Qsca are represented as solid, dashed, and dotted lines, respectively. (Reprinted with permission from P. K. Jain et al., J. Phys. Chem. B 2006, 110, 7238-7248.

The molar decadic absorption coefficient e is frequently called the extinction coefficient in published literature. Unfortunately numerical values of the extinction coefficient are often quoted without specifying units the absence of units usually means that the units are mol-1 dm3cm-1. See also [18]. The word extinction should properly be reserved for the sum of the effects of absorption, scattering, and luminescence. 

Fig. 6.9 Extinction spectrum (absorption + scattering) of polydispersed Ti02 aqueous solutions, with [P-25 Ti02] = 150 mg L" and pH 2 [redrawn from Salinaro et al. (1999), p. 329, Figure 6b].

The extinction, absorption, and scattering coefficients depend on catalyst particle concentration Cp. If concenfration is nof extremely high, this dependence is linear... 

Figure 6.1 Theoretical extinction, absorption and scattering spectra of silver NPs with radius 5,20 and 50nm, respectively.

Now consider the radiant energy traversing the length, ds, along the direction in which the intensity is delined a change in the intensity results from the combination of the effects of extinction (absorption and scattering) and emission ... 

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

Figure 15.1 illustrates the extinction, absorption, and scattering results from sample calculations performed for a common-sized nanoshell with a core diameter of 260 nm and a shell thickness of 20 nm immersed in water. The extinction peak observed in Fig. 15.1 is also known as the plasmonic resonance of the nanoshell. Plasmon is a result of the oscillation of incompressible electron gas molecules in the conducting gold shell. Such resonance can effectively alter the interference pattern... 

R = light reflected from the plate surface e = molar extinction (absorption) coefficient of the sample C = spot concentration S = plate scatter coefficient... 

Assuming the rate of energy incident on a particle of arbitrary shape is f, then the absorption, scattering and extinction efficiencies areQ =y/Jf, =(w ... 

Figure 2. Calculated absorption, scattering, and extinction cross-section from a 40 nm diameter Ag particle and a 60 nm diameter Au particle. The spectrum from the silver particle has a sharp resonance and its extinction is equally split between scattering and absorption components, udiereas, the 60 nm diameter gold particle has a broader resonance and is dominated by absorption.

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