Molar absorption coefficient

Definition: The molar (decadic) absorption coefficient (formerly: molar decadic extinction coefficient) is an intrinsic property of a given molecule (chromophore) or substance that describes how strongly that molecule/substance absorbs light at a particular wavelength. It is equal to absorbance (A, base 10) divided by the absorption pathlength, d, and the amount concentration, c: $\epsilon(\lambda) = -\frac{1}{cd}log_{10}(\frac{I_d}{I_0}) = \frac{A(\lambda)}{cd}$ It is generally represented by the unit $M^{-1}$ cm $^{-1} (=$ L mol $^{-1}$ cm $^{-1}$ .

Category: Physics

Related terms: optical density, modified beer-lambert law, attenuation, absorption of light

Abbreviation or symbol:

$epsilon$

Synonym: molar absorption coefficient, molar attenuation coefficient

References:

https://doi.org/10.1351/goldbook

https://doi.org/10.1351/goldbook.M03972

Alternative definition:

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