Absorption efficiency defined

The term Qext rises in value as d increases from near 0 for very small particles to 2 for larger particles. A scattering efficiency factor Q t and an absorption efficiency factor Qabs can each be defined in a manner similar to Qext. Then from Eq. 16.5... 

There are two more quantities that must be defined to complete the description of the fluidized bed combustor viz., the carbon combustion efficiency, ncCE> sulfur absorption efficiency, nsAE- These are ... 

The net result of absorption and scattering is extinction, while the light that is not extinct is said to be transmitted. In terms of the extinction efficiency, Q, which is defined as the ratio of the radiant power scattered and absorbed by a particle to the radiant power geometrically incident on the particle (proportional to the cross-sectional area). Therefore the extinction efficiency per cross-sectional area of the particle is the sum of its scattering and absorption efficiency per cross-sectional area, and Q, respectively ... 

Experimentally, the intensity of luminescence can be measured using a fluorescence spectrometer and expressed as the luminescence quantum efficiency (), defined as the ratio of the rate of luminescence to the rate of absorption (rate of light emitted/rate of light absorbed) ... 

Similarly, the absorption efficiency is defined as the fraction of the incident beam absorbed per unit cross-sectional area of particle. The total energy removed from the incident beam, the extinction energy, is the sum of the energy scattered and absorbed. The corresponding extinction efficiency is given by... 

Above the ionization threshold (see Chapter 8), the absolute photodissociation cross section can be obtained as the difference between the absolute total absorption cross section and the absolute photoionization cross section (see for example, for N2, Fig. 6 of Shaw, et ai, 1992). Another experimental quantity is the ionization efficiency defined as the total photoionization cross section divided by the total absorption cross section. 

There have been a few reports of II-VI and III-V heterojunction devices which have approached or even surpassed the performance of silicon cells. p-InP/n-CdS cells with a solar conversion efficiency of 12.5% have been fabricated.84 This good efficiency arises firstly because of the nature of InP the band gap is at 1.34 eV, which is optimal for the solar spectrum, and the transition is direct, so the absorption edge is steep. Secondly, there is an excellent crystal lattice match between InP and CdS, which means that almost fault-free junctions can be grown. p-CuInSe2/n-CdS cells which display current efficiencies (defined as electrons flowing in the short-circuit current per photon absorbed) of up to 70% between 550 and 1250 nm, and solar conversion efficiencies of ca. 5% have been made.85 p-CdTe/n-CdS cells of rather similar performance (current efficiency 85%, solar conversion efficiency 4.0%) have been produced without detailed attention to optimization of cell design, and it has been calculated that p-CdTe/n-ZiiaCdi-aS cells should be capable of a 41 44... 

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 solar energy absorption efficiency (VabsorpUon) is defined as the net rate at which energy is being absorbed by the solar reaetor divided by the solar power input through the aperture of the solar reactor. The... 

The previous assumptions together with the classical relationships of the different specific absorption rates, depending on the chemical reaction regime used to determine interfacial parameters, lead to the theoretical mean reduced values of the gaseous reactant in the gas exit stream and to absorption efficiency for a gas-liquid dispersion, where a is the geometrical specific interfacial area and Rl is the mean true liquid-side mass transfer coefficient defined for a bubble of diameter dg. ... 

It is customary to obtain fluorescence excitation spectra rather than absorption spectra in jets, where the total fluorescence intensity is monitored as a function of excitation laser wavelength. In cases where the fluorescence quantum efficiency (defined as fluorescence photons emitted/laser photons absorbed) is independent of excitation wavelength, the fluorescence excitation spectrum coincides with the absorption spectrum. Part of the fluorescence excitation spectrum of an Na2 jet operated with vibrational and rotational temperatures of 50 and 30 K, respectively, is shown in Fig. 4.3. The four intense bands arise from electronic transitions from v" = 0 in the ground state to v = 25... 

Some properties of the most used neutron absorber elements are reported in Table 15.3. The first parameter to be taken into account for the choice of a neutron absorber element is the adequacy between the local energy spectrum of the neutrons to be absorbed and the neutron absorption efficiency (the microscopic absorption cross-section) versus neutron energy of the nuclide. As an example (Fig. 15.3), cadmium has a very high absorption cross-section in the low-energy part of the neutron spectrum with a sharp decrease at about 0.5 eV (this cut-off is used to define the limit between the thermal and epithermal domains), whilst boron ( isotope) shows a smooth decrease on the whole neutron energy range [25]. The former will possibly be used (and is actually widely used) in thermal neutron reactors (PWR, BWR) the latter can be used in any kind of reactor, both as a neutron absorber or a burnable poison (e.g., borated glasses in PWR). 

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... 

When it is desired to compute, with rigorous methods, actual rather than equilibrium stages, Eqs. (13-69) and (13-94) can be modified to include the Murphree vapor-phase efficiency T ij, defined by Eq. (13-29). This is particularly desirable for multistage operations involving feeds containing components of a wide range ol volatility and/or concentration, in which only a rectification (absorption) or stripping action is provided and all components are not sharply separated. In those cases, the use of a different Murphree efficiency for each component and each tray may be necessary to compute recovery accurately. 

For this purpose, stabilization efficiency was defined as 1-As/Aq, where As and Aq represent the increase in absorbance in the blue spectral region (yellowing) in the presence and absence of stabilizer, respectively. The resulting stabilization efficiencies were found to decrease substantially over relatively short exposure times (ca. 40% decrease between 10 and 25 hrs irradiation). Difference absorption spectra obtained during accelerometer exposure exhibited a new absorption band at ca. 300 nm which overlapped strongly with polymer fluorescence (required for efficient RET quenching) and weakly with polymer absorption (screening).1... 

FRET can take place if the emission spectrum of the donor overlaps with the absorption spectrum of the acceptor and they are located at separation distances within 1-10 nm from each other. The efficiency of energy transfer E can be defined... 

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