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The SI unit of molar absorption coefficient is the square metre per mole (m 2 /mol), but in practice, quantities are usually expressed in terms of M −1 ⋅cm −1 or L⋅mol −1 ⋅cm −1 (the latter two units are both equal to 0.1 m 2 /mol).
absorption coefficient is essentially (but not quite always) synonymous with attenuation coefficient; see attenuation coefficient for details; molar absorption coefficient or molar extinction coefficient , also called molar absorptivity , is the attenuation coefficient divided by molarity (and usually multiplied by ln(10), i.e., decadic); see ...
Variable pathlength absorption spectroscopy uses a determined slope to calculate concentration. As stated above this is a product of the molar absorptivity and the concentration. Since the actual absorbance value is taken at many data points at equal intervals, background subtraction is generally unnecessary.
The Molar attenuation coefficient (also called "molar absorptivity"), which is the absorption coefficient divided by molarity (see also Beer–Lambert law) The mass attenuation coefficient (also called "mass extinction coefficient"), which is the absorption coefficient divided by density; The absorption cross section and scattering cross ...
Absorbance is defined as "the logarithm of the ratio of incident to transmitted radiant power through a sample (excluding the effects on cell walls)". [1] Alternatively, for samples which scatter light, absorbance may be defined as "the negative logarithm of one minus absorptance, as measured on a uniform sample". [2]
Therefore, measurements at two wavelengths yields two equations in two unknowns and will suffice to determine the amount concentrations c 1 and c 2 as long as the molar attenuation coefficients of the two components, ε 1 and ε 2 are known at both wavelengths. This two system equation can be solved using Cramer's rule.
In science, absorptivity may refer to: Molar absorptivity, in chemistry, a measurement of how strongly a chemical species absorbs light at a given wavelength; Absorptance, in physics, the fraction of radiation absorbed at a given wavelength; Emissivity § Absorptivity, information on the radiometrical aspect
These two different types of hemoglobin exhibit different absorption spectra that are normally represented in terms of molar extinction coefficients, as shown in Figure 1. The molar extinction coefficient of Hb has its highest absorption peak at 420 nm and a second peak at 580 nm. Its spectrum then gradually decreases as light wavelength increases.