{"term":{"id":"14091","title":"specific absorption coefficient","longtitle":"IUPAC Gold Book - specific absorption coefficient","doi":"10.1351\/goldbook.14091","code":"14091","status":"current","synonym":"<em>synonyms<\/em>: specific linear decadic spectral absorption coefficient, specific linear Napierian spectral absorption coefficient, specific spectral absorption coefficient","definitions":[{"id":1,"text":"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."},"sources":["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)"]}],"altoutputs":{"html":"https:\/\/goldbook.iupac.org\/terms\/view\/14091\/html","xml":"https:\/\/goldbook.iupac.org\/terms\/view\/14091\/xml","plain":"https:\/\/goldbook.iupac.org\/terms\/view\/14091\/plain"},"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","license":"The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/) for individual terms.","collection":"If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org .","disclaimer":"The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.","accessed":"2026-05-31T05:20:02+00:00"}}