Title: cage effect
Long Title: IUPAC Gold Book - cage effect
DOI: 10.1351/goldbook.C00771
Status: current

Definition
When in a condensed phase, or in a dense gas, reactant molecules come together, or species are formed in proximity to one another, and are caged in by surrounding molecules, they may undergo a set of collisions known as an encounter; the term 'cage effect' is then applied.The cage effect is also known as the Franck–Rabinowitch effect.

Related Terms
- cage: https://goldbook.iupac.org//terms/view/C00769
- encounter: https://goldbook.iupac.org//terms/view/E02086
- reactant: https://goldbook.iupac.org//terms/view/R05163

Source
- PAC, 1996, 68, 149. 'A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)' on page 155 (https://doi.org/10.1351/pac199668010149)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/C00771/html
- json: https://goldbook.iupac.org/terms/view/C00771/json
- xml: https://goldbook.iupac.org/terms/view/C00771/xml

Citation: Citation: 'cage effect' 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.C00771
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: 2026-06-29T13:37:07+00:00