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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 can, in turn, be written as a product of either a molar absorptivity of the absorber, ε, and the concentration c of absorbing species in the material, or an absorption cross section, σ, and the (number) density N of absorbers. (see Beer Lambert Law link for full derivation)
The spectrum of pure bilirubin is known, so the molar attenuation coefficient ε is known. Measurements of decadic attenuation coefficient μ 10 are made at one wavelength λ that is nearly unique for bilirubin and at a second wavelength in order to correct for possible interferences.
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]
Absorption peak (cm −1) Appearance C─H alkyl methyl 1260 strong 1380 weak 2870 medium to strong 2960 medium to strong methylene: 1470 strong 2850 medium to strong 2925 medium to strong methine: 2890 weak vinyl: C═CH 2: 900 strong 2975 medium 3080 medium C═CH 3020 medium monosubstituted alkenes: 900 strong 990 strong cis-disubstituted ...
Standard molar entropy, S o solid? J/(mol K) Heat capacity, c p? J/(mol K) Liquid properties Std enthalpy change of formation, Δ f H o liquid –25.4 kJ/mol Standard molar entropy, S o liquid: 253.80 J/(mol K) Enthalpy of combustion, Δ c H o –4549 kJ/mol Heat capacity, c p: 184.5 J/(mol K) at 25 °C Gas properties Std enthalpy change of ...
For a given medium at a given frequency, the opacity has a numerical value that may range between 0 and infinity, with units of length 2 /mass. Opacity in air pollution work refers to the percentage of light blocked instead of the attenuation coefficient (aka extinction coefficient) and varies from 0% light blocked to 100% light blocked:
Molar absorption coefficient (in mol −1 cm −1): links the quantity of absorbed light, at a given wavelength, to the concentration of fluorophore in solution. Quantum yield : efficiency of the energy transferred from incident light to emitted fluorescence (the number of emitted photons per absorbed photons).