Absorption coefficients, conversion factors

TABLE 3.4 Conversion Factors for Changing Absorption Coefficients from One Set of Units to Another... 

Table 3.4 gives conversion factors for converting absorption coefficients from one set of units to another and for changing between logarithms to the base 10 and base e. 

The ratio of the nonlinearity to the various absorption coefficients have been calculated using the conversion factor in equation 6 above. W is the figure of merit defined in reference 3, and given by -... 

With a representing the absorption cross section in cm per molecule (for the conversion to Ex see Tab. 3-2). To avoid any misinterpretations it is very important to state the origin of the absorption coefficients Ex and ax with respect to their logarithmic base as decadic or as Napierian (for conversions see Tab. 3-2). Many useful conversion factors for changing absorption coefficients from one set of units to another have been summarized by Finlayson-Pitts and Pitts (1986). To get a feeling for the magnitude of these values, several absorption coefficients and absorption cross sections of some molecules of environmental importance are presented in Tab. 3-6. 

In this expression J is dimensionless, the half-life has units of seconds and the twentieth-power term in the numerator is a conversion factor with units of moles/photon. The integral overlap of the lamp emission and the chromophore electronic spectrum, EexZx, defines light absorption in photons mole-1 sec-1. EX is the average extinction coefficient for a given wavelength Interval with Zx equaling the lamp output over this same band. 

Absorption Coefficient - In reference to a solar energy conversion devices, the degree to which a substance will absorb solar energy. In a solar photovoltaic device, the factor by which photons are absorbed as they travel a unit distance through a material. 

The oxidation of alkanes, alkenes and simple aromatics at 293 K under NOx rich tropospheric conditions has been studied using laser pulse initiation combined with cw laser long path absorption/LIF for the detection of OH and NO2. In the case of aliphatic hydrocarbons the absolute yield and the kinetics of the formation of these products have been found to be sensitive indicators for the reaction behaviour of the oxy radicals RO. In combination with mechanistic simulations rate constants for individual reactions as well as branching ratios have been derived, which permit the evaluation of the compound specific NO/NO2 conversion factors (NOCON - factors) for the first oxidation steps. In the case of benzene and toluene oxidation the results indicate that reaction of the primary formed X cyclohexa-dienyl radical (X = Cl, OH) with O2 is the dominant pathway, although the rate coefficients were found to be lower than 2 x 10" cmVs. 

In general, the design of hydrocarbon absorption systems is straightforward. Since mass U ansfer is not complicated by the occurrence of chemical reactions, conventional absorption coefficient, theoretical plate, and absorption factor concepts can be used for design calculations (see Chapter I). Basic data for such calculations, including the thermodynamic properties of compounds found in coke-oven gas and equilibrium data for several gas-coal liquid systems, are given in the U.S. DOE Coal Conversion Systems Data Book (1982) and other hydrocarbon data compendia. 

The extinction coefficient is used in conventional spectrophotometry and measured in the traditional units of L mol em. It can be related by a conversion factor to a quantity from physics, the absorption... 

---