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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 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 ...
Thus a scattering coefficient μ s and an absorption coefficient μ a can be combined into a total extinction coefficient μ = μ s + μ a. [ 6 ] Importantly, Beer also seems to have conceptualized his result in terms of a given thickness' opacity, writing "If λ is the coefficient (fraction) of diminution, then this coefficient (fraction) will ...
The SI unit of mass attenuation coefficient is the square metre per kilogram (m 2 /kg). Other common units include cm 2 /g (the most common unit for X-ray mass attenuation coefficients) and L⋅g −1 ⋅cm −1 (sometimes used in solution chemistry). Mass extinction coefficient is an old term for this quantity. [1]
A. R. Forouhi and I. Bloomer deduced dispersion equations for the refractive index, n, and extinction coefficient, k, which were published in 1986 [1] and 1988. [2] The 1986 publication relates to amorphous materials, while the 1988 publication relates to crystalline.
At a wavelength of 260 nm, the average extinction coefficient for double-stranded DNA is 0.020 (μg/mL) −1 cm −1, for single-stranded DNA it is 0.027 (μg/mL) −1 cm −1, for single-stranded RNA it is 0.025 (μg/mL) −1 cm −1 and for short single-stranded oligonucleotides it is dependent on the length and base composition.
For each species and wavelength, ε is a constant known as the molar absorptivity or extinction coefficient. This constant is a fundamental molecular property in a given solvent, at a particular temperature and pressure, and has units of 1 / M ∗ c m {\displaystyle 1/M*cm} .