Term: absorptance, \(\alpha\)
https://doi.org/10.1351/goldbook.A00035

Definition:
Ratio of the absorbed to the incident radiant power. Also called absorption factor. When α ≤ 1, α ≈ Ae, where Ae is the Napierian absorbance.

Related Terms:
1) radiant power (http://doi.org/10.1351/goldbook.R05046).
2) absorption factor (http://doi.org/10.1351/goldbook.A00039).
3) absorbance (http://doi.org/10.1351/goldbook.A00028).

Source: Green Book, 2nd ed., p. 32 (https://goldbook.iupac.org/files/pdf/green_book_2ed.pdf)

Citation: 'absorptance, \(\alpha\)' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.A00035

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