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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.
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
ε is the molar attenuation coefficient of that material, and; c(z) is the molar concentration of that material at z. If c(z) is uniform along the path, the relation becomes =. The use of the term "molar absorptivity" for molar attenuation coefficient is discouraged. [1]
Extinction coefficient refers to several different measures of the absorption of light in a medium: Attenuation coefficient, sometimes called "extinction coefficient" in meteorology or climatology Mass extinction coefficient, how strongly a substance absorbs light at a given wavelength, per mass density
The attenuation coefficient (NB used infrequently with meaning synonymous with "absorption coefficient") [citation needed] The Molar attenuation coefficient (also called "molar absorptivity"), which is the absorption coefficient divided by molarity (see also Beer–Lambert law)
When an isosbestic plot is constructed by the superposition of the absorption spectra of two species (whether by using molar absorptivity for the representation, or by using absorbance and keeping the same molar concentration for both species), the isosbestic point corresponds to a wavelength at which these spectra cross each other.