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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 ...
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.
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
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 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. On the other hand, H b O 2 {\displaystyle HbO2} shows its highest absorption peak at 410 nm, and two secondary peaks at 550 nm and 600 nm.
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
A common expression of the Beer's law relates the attenuation of light in a material as: =, where is the absorbance; is the molar attenuation coefficient or absorptivity of the attenuating species; is the optical path length; and is the concentration of the attenuating species.