14010 IUPAC Gold Book - extrinsic absorption 10.1351/goldbook.14010 14010 current 1 Absorption of ultraviolet, visible, or infrared radiation in semiconductors and insulators corresponding to optical transitions of electrons from defect energy levels (within the bandgap energy) to conduction band levels, or holes to valence band levels (photoionisation of defects), or from the ground state level to excited levels of a given intrinsic defect of any sort. Typically, extrinsic absorption bands are a few tenths to a few \(\pu{eV}\) distant from the fundamental absorption edge in semiconductors and insulators. The red limits of photocatalytic reactions are determined by photoexcitation of photocatalysts in the extrinsic absorption bands. Doping of a catalyst creates an extrinsic defect. fundamental absorption edge https://goldbook.iupac.org//terms/view/14017 intrinsic defect https://goldbook.iupac.org//terms/view/14026 PAC, 2011, 83, 931. 'Glossary of terms used in photocatalysis and radiation catalysis (IUPAC Recommendations 2011)' on page 951 (https://doi.org/10.1351/PAC-REC-09-09-36) https://goldbook.iupac.org/terms/view/14010/html https://goldbook.iupac.org/terms/view/14010/json https://goldbook.iupac.org/terms/view/14010/plain Citation: 'extrinsic absorption' 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.14010 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. If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org . 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. 2026-05-07T00:06:30+00:00