Title: specific absorption coefficient
Long Title: IUPAC Gold Book - specific absorption coefficient
DOI: 10.1351/goldbook.14091
Status: current

Definition
Linear napierian, \(\alpha_{\lambda}^{\ast}\), or linear decadic, \(a_{\lambda}^{\ast}\), absorption coefficient divided by the mass concentration, \(\rho\).

Notes
1) The asterisk as superscript indicates that it is a specific property.
2) Absorption coefficient is always a spectral property; the subscript \(\lambda\) may be omitted but the wavelength should be specified.
3) Mathematical definition: \[\alpha_{\lambda}^{\ast} = \frac{\alpha_{\lambda}}{\rho} \quad {\rm{or}} \quad a_{\lambda}^{\ast} = \frac{a_{\lambda}}{\rho}\] SI unit is \(\pu{m kg-1}\) , common unit is \(\pu{m g-1}\) or \(\pu{cm2 g-1 nm-1}\).
4) For reacting systems with mass fluctuations and high scattering, space- and time-dependent specific, napierian and decadic, absorption coefficients are necessary, i.e., \(\alpha_{\lambda}^{\ast}(\boldsymbol{x},t)\) and \(a_{\lambda}^{\ast}(\boldsymbol{x},t)\), respectively; \(\boldsymbol{x}\) defines the position in a three-dimensional space.

Source
- PAC, 2011, 83, 931. 'Glossary of terms used in photocatalysis and radiation catalysis (IUPAC Recommendations 2011)' on page 989 (https://doi.org/10.1351/PAC-REC-09-09-36)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/14091/html
- json: https://goldbook.iupac.org/terms/view/14091/json
- xml: https://goldbook.iupac.org/terms/view/14091/xml

Citation: Citation: 'specific absorption coefficient' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.14091
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Accessed: 2026-05-31T05:20:02+00:00