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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).
The absorption coefficient of a volume, denoted μ a, and the scattering coefficient of a volume, denoted μ s, are defined the same way as the attenuation coefficient. [ 6 ] The attenuation coefficient of a volume is the sum of absorption coefficient and scattering coefficients: [ 6 ]
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 ...
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]
Planck opacity (also known as Planck-Mean-Absorption-Coefficient [1]) uses the normalized Planck black-body radiation energy density distribution, (), as the weighting function, and averages directly: = () = (), where is the Stefan–Boltzmann constant.
Mass attenuation coefficients of selected elements for X-ray photons with energies up to 250 keV. The mass attenuation coefficient, or mass narrow beam attenuation coefficient of a material is the attenuation coefficient normalized by the density of the material; that is, the attenuation per unit mass (rather than per unit of distance).
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
Spectral hemispherical attenuation coefficient: μ ν μ λ: m −1: Spectral radiant flux absorbed and scattered by a volume per unit length, divided by that received by that volume. Directional attenuation coefficient: μ Ω: m −1: Radiance absorbed and scattered by a volume per unit length, divided by that received by that volume.