14002 IUPAC Gold Book - colour centres 10.1351/goldbook.14002 14002 current mentioned: surface F centre, surface V centre 1 Lattice defects (typically vacancies) that trap one or more electrons or holes in ionic crystals. They constitute a long-lived deep trap with a low efficiency of trapping of a carrier of the opposite sign. Colour centres accumulate in irradiated solids and give rise to photoinduced extrinsic absorption bands (photoinduced colour) in semiconductors and insulators. The dominant decay pathway of colour centres upon irradiation at moderate temperatures is photoionisation with the formation of free carriers and empty traps. The surface F (anion vacancies occupied by electrons) and V centres (trapped holes) in semiconductors and insulators are also colour centres with the distinction that they act as metastable active states of photocatalytic centres. Monitoring the photocolouration of a metal oxide during a surface photochemical reaction probes whether the reaction is photocatalytic. energy trap https://goldbook.iupac.org//terms/view/14003 extrinsic absorption bands https://goldbook.iupac.org//terms/view/14010 free carriers https://goldbook.iupac.org//terms/view/14014 photocatalytic centres https://goldbook.iupac.org//terms/view/14043 PAC, 2011, 83, 931. 'Glossary of terms used in photocatalysis and radiation catalysis (IUPAC Recommendations 2011)' on page 945 (https://doi.org/10.1351/PAC-REC-09-09-36) https://goldbook.iupac.org/terms/view/14002/html https://goldbook.iupac.org/terms/view/14002/json https://goldbook.iupac.org/terms/view/14002/plain Citation: 'colour centres' 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.14002 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. 2026-06-29T09:59:03+00:00